United States Patent (19) 11 Patent Number: 4,540,564 Bodor (45) Date of Patent: Sep. 10, 1985

54 BRAIN-SPECIFICDRUG DELIVERY 57 ABSTRACT 75 Inventor: Nicholas S. Bodor, Gainesville, Fla. The subject compounds, which are adapted for the site-specific/sustained delivery of centrally acting drug 73) Assignee: University of Florida, Gainesville, species to the brain, are: Fla. (a) compounds of the formula 21 Appl. No.: 516,382 22 Filed: Jul. 22, 1983 D-DHC) (I) Related U.S. Application Data wherein D is a centrally acting drug species, and 63 Continuation-in-part of Ser. No. 379,316, May 18, DHC is the reduced, biooxidizable, blood-brain 1982, Pat. No. 4,479,932, Ser. No. 461,543, Jan. 27, barrier penetrating lipoidal form of a dihydropyri 1983, , and Ser. No. 475,493, Mar. 15, 1983, , said Ser. dine - pyridinium salt redox carrier, with the No. 46,543, and Ser. No. 475,493, each is a continua proviso that when DHC) is tion-in-part of Ser. No. 379,316. 30 Foreign Application Priority Data O May 12, 1983 WO, PCT Int'l Appl...... WO83/00725 May 16, 1983 ICA) Canada ...... 42892 51) Int. Cl...... A61K 49/00; A61K 31/58; r’sN CO7J 17/00 52 U.S. Cl...... 424/9; 260/239.5; R 514/176 58 Field of Search ...... 424/9, 241; 260/239.5 wherein R is lower alkyl or benzyl and D is a drug species containing a single NH2 or OH func 56 References Cited tional group, the single OH group when present U.S. PATENT DOCUMENTS being a primary or secondary OH group, said drug species being linked directly through said NH2 or

3,962,447 6/1976 Higuchi et al...... 424/263 4,035,507 7/1977 Bodor et al...... 424/319 OH functional group to the carbonyl function of 4,065,566 12/1977 Bodor et al. ... 424/266 DHC), then D must be other than a sympathetic 4,479,932 10/1984 Bodor ...... 424/9 stimulant, steroid sex hormone or long chain alka noi; and OTHER PUBLICATIONS (b) non-toxic pharmaceutically acceptable salts of Bodor et al., Science, vol. 214 (1981) 1370-2. compounds of formula (I) wherein D is a cen Bodor et al., J. Pharm. Sci., 67 (1978) 685-7. trally acting drug species and DHC is the re Bodor et al., J. Med. Chem., 26 (1983) 313-8. duced, biooxidizable, blood-brain barrier penetrat Bodor et al., J. Med. Chem., 26 (1983) 528-34. ing lipoidal form of a dihydropyridine - pyridin Sher et al., J. Med. Chem., 19 (1976) 113-7. ium salt redox carrier. The corresponding ionic Bodor et al., J. Pharm. Sci. 67 (1978) 1045-50. pyridinium salt type drug/carrier entities D Chem. and Eng. News, 12/21/81, 24-25. QCY are also disclosed. Primary Examiner-Christine M. Nucker Attorney, Agent, or Firm-Dennis P. Clarke 86 Claims, 8 Drawing Figures U.S. Patent Sep. 10, 1985 Sheet 1 of 8 4,540,564

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S S S Se S S S a of AM/F fissue of Azovo 4,540,564 1. 2 is interesting that there are areas within the brain, such BRAIN-SPECIFC DRUG DELVERY as the subfornical body and the postremia in which the capillary cells are not closely linked so that they lack CROSS-REFERENCE TO RELATED the characteristics of the BBB. They provide the entry APPLICATIONS of small amounts of compounds which would not ordi This application is a continuation-in-part of my ear narily enter the barriers. Hoffmann and Olszewzki, lier copending applications Ser. No. 379,316, filed May Neurology (Minneap.), 11, 1081 (1961). 18, 1982, now U.S. Pat. No. 4,479,932 Ser. No. 461,543, Foreign compounds which enter organs other than filed Jan. 27, 1983, and Ser. No. 475,493, filed Mar. 15, the central nervous system with ease, may penetrate the 1983; Ser. No. 461,543 and Ser. No. 475,493 are them 10 CNS slowly or hardly at all. A number of theories con selves continuations-in-part of Ser. No. 379,316. All cerning the nature of the barrier have been proposed. three earlier copending applications are hereby ex The widely accepted concept describes the boundary as pressly incorporated by reference herein in their entire a fat-like layer interspersed with small pores, although ties and relied upon. the BBB is not a simple, anatomically well-defined uni 15 FIELD OF THE INVENTION tary physical entity. Shuttleworth, Prog. Exp. Tumor Res., 17, 279 (1972). Penetration of such a barrier may The present invention relates to a dihydropyridine/- occur by several processes: lipid soluble substances may pyridinium salt type of redox system for the site-specific passively penetrate into the cells, while small molecules or sustained delivery (or both) of a wide variety of drug such as water and urea may pass through the pores. In species to the brain. More especially, this invention 20 addition to these simple physical processes, carrier relates to the discovery that a biologically active com mediated and active transport processes govern the pound coupled to a lipoidal carrier moiety comprising a movement of many molecules through the BBB. Thus, dihydropyridine nucleus readily and easily penetrates it is generally accepted that lipid solubility, degree of the blood-brain barrier ("BBB') and attains increased levels of concentration in the brain; oxidation of the 25 ionic dissociation or protonation and the ability of tem dihydropyridine carrier moiety in vivo to the ionic porary combination with membrane constituents affect pyridinium salts prevents its elimination from the brain, delivery through the BBB. It has been shown, for exam while elimination from the general circulation is accel ple, that in the class of barbiturates, a quantitative corre erated, resulting in significant and prolongedly sus lation could be established between their ease to pass tained brain-specific drug activity, whether ascribable 30 into the brain (as reflected by the different times of to the cleavage of the D-QC entity and sustained onset of anesthetic action) and their lipid/water parti release of the drug in the brain and/or to D-QC tion coefficient. Mark et al, J. Pharmacol and Exp. itself. Therap, 123, 79 (1957). The role of lipid solubility in drug penetration through the BBB is also exemplified BACKGROUND ART 35 by the better absorption of the sparingly water-soluble The delivery of drug species to the brain is ofttimes thiamine propyl disulfide (TPD) as compared to the seriously limited by transport and metabolism factors water-soluble thiamine hydrochloride (THCl). and, more specifically, by the functional barrier of the Thomson et al, Ann. Int. Med., 74, 529 (1971). Some endothelial brain capillary well deemed the blood-brain materials such as glucose and amino acids are trans barrier, BBB. Site-specific delivery and sustained deliv ported by active mechanism, characterized by satura ery of drugs to the brain are even more difficult, and to tion, bidirectional molecular specificity, bidirectional date no useful simple or generic techniques to achieve competitive inhibition and bidirectional countertran such phenomena are known to the art. sport. Fishman, Am J. Physiol, 206, 836 (1964). Indeed, the barriers separating plasma from the brain Changes in permeability of the BBB can be caused by and cerebrospinal fluid (CSF) are complex systems 45 several pathological and toxicological processes. Par involving passive and active transport and subserve a dridge, Connor and Crawford, CRC Crit. Rev. Toxicol., number of important functions. The boundary between 179 (1975). A general increase in the barrier permeabil plasma and the central nervous system (CNS) is much ity, such as a nonspecific breakdown of the barrier has, less permeable than that between plasma and other however, severe consequences, including cerebral tissue cells to a variety of water soluble substances, such 50 edema. as organic electrolytes, organic acids and bases, as well It too is well documented that the BBB is relatively as to large molecules such as proteins. Such a barrier impermeable to the ionized forms of drugs and other also provides a path for clearance from the brain of the molecules. Drugs which are weak organic electrolytes breakdown products of cellular metabolism. The CNS appear to pass from blood to CSF to reach a steady state and its fluids can be considered basically a three-com 55 ratio characteristic of each molecule according to its partment system: the blood or the plasma, CSF and pKa and the existence of a normal pH gradient between brain tissue. There is a diffusion-controlled exchange blood and CSF. It is clear that it is the most difficult for between CSF and the extracellular fluid (CF) of the quaternary pyridinium or ammonium salts to penetrate brain. It has also been suggested that the permeabilities the BBB. of blood-CSF and blood-brain barriers are practically And removal of substances from the brain and CSF is identical with respect to drugs and other foreign sub obviously a significant factor in regulating drug concen stances. Mayer et al, J. Pharmacol. and Exp. Therap, trations in the CNS. There are several efflux processes: 125, 185 (1959). bulk flow via the arachnoid villi, diffusion of lipid solu The BBB is, moreover, basically the result of the fact ble substances into brain and blood, active transport and that the endothelial cells in the brain capillaries are 65 metabolism by adjacent meninges. Once a drug or me joined by continuous, tight intercellular junctions, such tabolite enters the CSF from blood or brain by simple that material has to pass through the cells rather than diffusion, it may rapidly be removed, either by nonse between them in order to move from blood to brain. It lective bulk flow or by active transport mechanism 4,540,564 3 4. associated with the choroid plexus or other nondefined chemical transformations would be needed to link any structures in the CSF compartment. It is generally ac specific antitumor agent (or indeed any specific drug) to cepted that highly lipid-soluble drugs leave the CSF an appropriate carrier moiety. more rapidly than poorly lipid-soluble ones, but the Accordingly, acutely serious need exists in this art for barrier to passage of compounds from CSF has only a truly effective generic but nonetheless flexible method superficial similarity to the blood-CSF barrier. for the site-specific, or sustained delivery, or both, of Drug elimination processes from the brain are signifi drug species to the brain, while at the same time avoid cantly directly related to drug accumulation in the ing the aforesaid noted and notable disadvantages and brain. It is generally assumed that efflux in the opposite drawbacks associated with penetration of the blood direction involves almost the same processes as for 10 brain barrier, with dihydropyridine latentiated prodrug entry, except that the role of the bulk flow and the forms of drug species themselves comprising a pyridin metabolic processes in the brain are not to be over ium salt active nucleus, and with the necessity for intro looked. ducing critically coordinated and designed, release rate The two elimination processes studied in the earlier controlling substituents onto any particular drug carrier literature and which can be said to have a certain bear 15 moiety. ing on the present invention involve elimination from It is also known to this art that Parkinsonism, a stria the brain of ionic species. Thus, it is found that non tal dopamine deficiency syndrome H. Ehringer and O. metabolized inonic species, such as the acetate ion, have Hornykiewicz, Klin. Wsch, 38, 1236 (1960), cannot be a three times slower elimination rate from the CSF than treated directly with dopamine, for dopamine and re from the blood. Freundt, Arz, Forsch, 23, 949 (1973). 20 lated catecholamines also do not cross the blood-brain An even more dramatic change in the elimination rate barrier B. E. Roos and G. Steg, Life Sci, 3,351 (1964)). was found in the case of a quaternary piperidinium salt. L-Dopa, considered as a prodrug for dopamine, was The quaternary salt, formed in situ after delivery of a first discovered to be useful in the treatment of Parkin haloalkylamine, which undergoes cyclization to the sonism more than twenty years ago A. Barbeau, Ex quaternary salt, in the brain, as well, was found to have 25 cepta Medica, Int. Congr. Ser. 38, 152 (1961); W. Birk an at least ten times slower elimination rate from the mayer and O. Hornykiewicz, Wien. Klin. Wochnenschr, brain than from the rest of the body. It was concluded 73, 787 (1961). Indeed, L-Dopa is considered to be the by the authors (Ross and Froden, Eur, J. Pharmacol, best available treatment for Parkinsonism, but, unfortu 13,461970) that the outflow rate of the quaternary salt nately, at the expense of a wide variety of undesirable corresponded to the inflow rate. Similar results were 30 side effects A. Barbeau, TIPS, 2, (11), 297 (1981)). The obtained for the erythrocytes: the efflux of the quater peripheral side effects of L-Dopa, which range from nary salt was very slow. Ross, J. Pharm. Pharmacol., 27, nausea and vomiting to cardiac arrythmias and hypo 322 (1975). tension, appear to be due to one or more of the meta And while it too has been suggested to deliver a drug bolic products thereof, rather than L-Dopa per se. L species, specifically N-methylpyridinium-2-carbaldox 35 Aromatic amino acid decarboxylase enzyme is responsi ime chloride (2-PAM), into the brain, the active nucleus ble for the major metabolism of L-Dopa, whether prior, of which in and of itself constituting a quaternary pyri during or after absorption. Concurrent administration dinium salt, by way of the dihydropyridine latentiated of L-Dopa with an inhibitor of aromatic amino acid prodrug form thereof, such approach is conspicuously decarboxylase, which should not be able to penetrate delimited to relatively small molecule quaternary pyri the BBB, reduces the decarboxylation of L-Dopa in dinium ring-containing drug species and does not pro peripheral tissues. Such reduction allows higher pro vide the overall ideal result of brain-specific, sustained portions of L-Dopa to reach the CNS and at the same release of the desired drug, with concomitant rapid time diminishes the peripheral side effects considerably, elimination from the general circulation, enhanced drug particularly vomiting and cardiac arrythmias, but a efficacy and decreased toxicity. Hence, no “trapping" 45 number of serious side effects still persist A. Barbeau, in the brain of the 2-PAM formed in situ results, and TIPS, supra; A. Barbeau and M. Roy, Neurology, 26, 399 obviously no brain-specific, sustained delivery occurs as (1976). Attempts have also been made to alleviate the any consequence thereof; the 2-PAM is eliminated as well-known dissolution, absorption and metabolism fast from the brain as it is from the general circulation problems of L-Dopa H. Ninterberger, Biochem. Med., and other organs. Compare U.S. Pat. Nos. 3,929,813 and 50 5, 412 (1971); H. Shindo, T. Komai, K. Tanaka, E. 3,962,447; Bodor et al., J. Pharm. Sci, 67, No. 5, 685 Nakajima and N. Miyakoshi, Chem. Pharm. Bull., 21, (1978). See also Bodor, “Novel Approaches for the 826 (1973); C. O. Rutledge and M. M. Hoehn, Nature Design of Membrane Transport Properties of Drugs", (London), 244, 447 (1973); R. L. Bronaugh, R. J. in Design of Biopharmaceutical Properties Through Pro McMurty, M. M. Hoehn and C. O. Rutledge, Biochem. drugs and Analogs, Roche, E. B. (ed.), APhA Academy 55 Pharmacol, 24, 1317 (1975), employing prodrug ap of Pharmaceutical Sciences, Washington, D.C., 98-135 proaches N. Bodor, K. B. Sloan, T. Higuchi and K. (1976). It has also been speculated to deliver, e.g., an Sasahara, J. Med. Chenn., 20, 1435 (1977); A. M. Felix, antitumor agent into the brain by utilizing a dihy D. P. Winter, S. S. Wang, I. D. Kulesha, W. R. Pool, D. dropyridine/pyridinium redox carrier moiety therefor, L. Hane and H. Sheppard, J. Med. Chem., 17, 422 but this particular hypothesis necessarily entails deriva (1974). tizing the dihydropyridine/pyridinium carrier with a Additionally, dopamine agonists, which are used in substituent R itself critically designed to control the the treatment of hyperprolactinemia associated with release rate of the active drug species from the quater pituitary adenomas or amenorrhea R. F. Spark and G. nary drivative thereof, as well as being critically func Dickenstein, Ann. Int. Med., 90,949 (1979), also induce tionally coordinated with the particular chemical and 65 unwanted side effects. therapeutic activity/nature of the antitumor drug spe Thus, especially acutely serious need exists in this art cies itself; Bodor et al, J. Pharm. Sci, supra. Moreover, to delivery a dopaminergic agent directly and specifi the hypothesis does not include any indication of what cally to the brain, in a sustained manner, and there elicit 4,540,564 5 6 the desired dopaminergic response, e.g., for the treat -continued ment of the Parkinsonism or hyperprolactinemia. Scheme : BBB, blood-brain barrier. D-QC - Enzymatic Enzymatic (D-QC SUMMARY AND OBJECTS OF THE in the brain cleavage cleavage k in circulatory system INVENTION 4 Accordingly, a major object of the present invention -- k3 is the provision of a generic method for the specific (D) + (QC) D)D +-- (QC)1QC and/or target enhanced delivery to the brain of a wide variety of drug species and to achieve brain-specific 10 drug delivery by effecting the bidirectional transport of BBB the drug species into and out of the brain employing dihydropyridine-pyridinium salt carrier type redox systems. Elimination Another object of the invention is to provide for 5 brain specific drug delivery utilizing a dihy Consistent with the foregoing Scheme 1, any drug spe cies D is coupled to a quaternary pyridinium salt car dropyridine-pyridinium salt carrier type redox system, rier QC+ and the prodrug (D-QC+ which results is which drug/carrier system is characterized by en then reduced chemically to the lipoidal dihydro pro hanced drug efficacy and decreased toxicity. Indeed, 20 prodrug form D-DHC). Alternativey, the drug species consistent herewith systemic toxicity is significantly (D) can be directly coupled to the dihydro carrier reduced by accelerating the elimination of the drug/- DHC in certain instances to yield said pro-prodrug quaternary carrier system, and even central toxicity is form (D-DHC). After administration of the D-DHC in reduced by providing a low level, sustained release of 25 vivo, it is rapidly distributed throughout the body, in the active drug species in the brain. cluding the brain. The dihydro form D-DHC) is then in Yet another object of this invention is the provision situ oxidized (rate constant, k) (by the NAD-2NADH of a chemical delivery system for the site-specific and system) to the ideally inactive original D-QCF quater sustained release of drug species to the brain, and one in nary salt prodrug, which, because of its ionic, hydro 30 philic character, is rapidly eliminated from the general which a special pro-prodrug reduced form of an active circulation of the body, while the blood-brain barrier drug species is actually delivered to the body of a pa prevents its elimination from the brain k3) > k2; tient, not a prodrug as such and not a drug/carrier k3>>k7). Enzymatic cleavage of the D-QC that is entity necessarily comprised of critically tailored re "locked' in the brain effects a sustained delivery of the lease rate-controlling substituent(s). 35 drug species D), followed by its normal elimination Yet another object of this invention is to provide (k5), metabolism. A properly selected carrier QC enhanced delivery to the brain of a wide variety of will also be rapidly eliminated from the brain centrally acting agents which are not themselves able to (ké) >k2). Because of the facile elimination of penetrate the blood-brain barrier to any considerable D-QC) from the general circulation, only minor 40 amounts of drug are released in the body (k3) > k4); extent. D is released primarily in the brain (k4) k2). The over Briefly, the present invention features a dihy all result is a brain-specific, sustained release of the dropyridine-pyridinium salt carrier redox system for target drug species. Cf. Bodor et al, Science, 214, 1370 the specific and sustained delivery of drug species to the (1981); C&EN, 24 (Dec. 21, 1981). brain according to the following Scheme i: 45 In accord with the foregoing, the present invention provides compounds adapted for the site-specific/sus tained delivery of a centrally acting drug species to the Scheme 1: BBB, blood-brain barrier. brain, said compounds being: D) + (DHC) chemicalcoupling (a) compounds of the formula 50 Or D-DHC) (I) (D) + (QC)." couplingEis (D-QCities (D-DHC) wherein D is a centrally acting drug species, and DHC) is the reduced, biooxidizable, blood-brain bar 55 rier penetrating lipoidal form of a dihydropyridine Delivery pyridinium salt redox carrier, with the proviso that when DHC) is

O k 4. /Elimination D-DHC) D-DHC) in the brain in circulatory system r and organs N 65 R in vivo in vivo k1 oxidation k1 oxidation wherein R is lower alkyl or benzyl and D) is a drug species containing a single NH2 or OH functional 4,540,564 7 8 group, the single OH group when present being a pri and non-toxic pharmaceutically acceptable salts mary or secondary OH group, said drug species being thereof, wherein D is a dopamine having the struc linked directly through said NH2 or OH functional tural formula group to the carbonyl function of DHC), then D must be other than a sympathetic stimulant, steroid sex hor YO NH2 mone or long chain alkanol; or (b) non-toxic pharmaceutically acceptable salts of 10 YO compounds of formula (I) wherein (D) is a centrally acting drug species and DHC) is the reduced, biooxi in which each Y is independently hydrogen or a hydro dizable, blood-brain barrier penetrating lipoidal form of lytically or metabolically cleavable hydroxyl protective a dihydropyridine-pyridinium salt redox carrier. In 15 group, and DHC) is the reduced, biooxidizable, blood brain barrier penetrating, lipoidal form of a dihy another aspect, the present invention provides com dropyridine-pyridinium salt redox carrier. In still an pounds having the formula other aspect, the present invention provides compounds 20 (D-QC+Y- (II) having the formula (D-QC+Y- (II) wherein Y- is the anion of a non-toxic pharmaceuti cally acceptable acid, D) is a centrally acting drug 25 wherein Y is defined above and D) is a dopamine species and QC is the hydrophilic, ionic pyridinium having the structural formula salt form of a dihydropyridine-2-pyridinium salt redox carrier, with the proviso that when QCF is 30 YO NH2

YO

35 in which each Y is independently hydrogen or a hydro (Or lytically or metabolically cleavable hydroxyl protective iN R group, and QC+ is the hydrophilic, ionic pyridinium salt form of a dihydropyridine-pyridinium salt redox wherein R is lower alkyl or benzyl and D is a drug 40 carrier. species containing a single NH2 or OH functional Briefly, one presently preferred chemical delivery group, the single OH group when present being a pri system for dopamine according to this invention has the structure (2) in the following Scheme 2, and wherein mary or secondary OH group, said drug species being 45 linked directly through said NH2 or OH functional the amino function of dopamine is appropriately linked group to the carbonyl function of QC, then D must to the dihydropyridine-type carrier system, while the be other than a sympathetic stimulant, steroid sex hor catechol function is advantageously protected, for ex 50 ample, as a corresponding ester function, e.g., the mone or long chain alkanol. The present invention fur dipivalyl ester illustrated. The brain-specific delivery of ther provides a generic method for specific and/or dopamine, or the otherwise eliciting of a dopaminergic target enhanced delivery to the brain of a wide variety response, requires a succession of processes, including of centrally acting drug species, such brain-specific 55 oxidation of the dihydropyridine ring to the corre drug delivery being effected via the bidirectional trans sponding pyridinium salt (for example, structure 3), port of the drug species into and out of the brain by which provides the basis for "locking-in' the brain the means of dihydropyridine-pyridinium salt carrier type molecule, hydrolysis of the, e.g., pivalyl esters (see redox systems. 60 structure 4) likely via the 3- and/or 4-monopivalyl es In yet another aspect, the present invention provides, ters and, finally, the release of dopamine (1) from 4, as an effective dopaminergic chemical delivery system, which can be either a hydrolysis or a reductive process compounds having the formula a possible reductive release of dopamine was very 65 recently suggested by a model for a presynaptic termi D-DHC) (I) nal, L. L. Miller, A. N. K. Lau and E. K. Miller, J. Am. Chem. Soc., 104,5242 (1982). 4,540,564 9 10

Scheme 2: OH OCOC(CH3)3 OR OH OCOC(CH3)3 OR chemical G in vivo G transformations hydrolysis and oxidation CH CH2 CH2 (H, CH-NH-CO th: NH2 - O

R A R2 E or COC(CH3)3

in vivo cleavage in -1 the brain

OH elimination G from general OH circulatory system CH2heroid -- CH3 ternary dopamine precursor 6a (O) in 20% liver ho As per the above Scheme 2, for the brain specific 40 mogenate; delivery of dopamine (1), structure 2 is one chemical FIG. 5 is a semilog plot of peak heights of 1-methyl-3- delivery system consistent herewith, and 4 is one pre {N-Ig-(3,4-dipivalyloxyphenyl)ethyl)-carbamoyl-1,4- cursor locked in the brain and eliminated rapidly from dihydropyridine 5c against time in plasma (O), brain the rest of the body. Structures 3 depicts intermediates homogenate (A), whole blood (O) and liver homoge formed during the stepwise hydrolysis and oxidation 45 nate (O); processes. FIG. 6 is a graph plotting concentrations against time of 1-methyl-3-(N-A-(3,4-dihydroxyphenyl)ethylcar BRIEF DESCRIPTION OF THE DRAWINGS bamoyl pyridinium cation (6a) in brain (O) and in blood FIG. 1 is a graph plotting the time course of 1-meth (O) following administration of 1-methyl-3-(N-R-(3,4- yl-3-(N-Ig-(3,4-dipivalyloxyphenyl)ethyl-carbamoyl 50 dipivalyloxyphenyl)-ethyl)carbamoyl-1, 4-dihy 1,4-dihydropyridine 5c (O) and its products, monopiva dropyridine (5c), with the error bars indicating SEM; lyl-dihydro derivative 11 (v), the dihydrodopamine FIG. 7 is a graph plotting the effects of compounds 5c derivative 5a (A) and the quaternary dopamine precur (A) and 6a (O) administered I.V. at 1 mg/kg dose level, sor 6a (O) in plasma; bn the serum prolactin levels in rats; and FIG. 2 is a graph plotting the time course of 1-meth 55 FIG. 8 is a graph plotting concentrations with stan yl-3-(N-ER-(b 3,4-dipivalyloxyphenyl)ethyl)-carbam dard errors against time for testosterone-17-nicotinate oyl-1,4-dihydropyridine 5c (O) and its products, N-methyl cation, calculated as iodide, in brain (O) and monopivalyl-dihydro drivative 11 (v) and the quater in blood (O) and concentration of released testosterone nary dopamine precursor 6a (O) in whole blood; (ng/g) in brain (V), all following administration of the FIG. 3 is a graph plotting the time course of 1-meth corresponding dihydropyridine compound. Also plot yl-3-(N-A-(3,4-dipivalyloxyphenyl)ethyl)-carbamoyl ted are concentrations of testosterone in brain (O) and 1,4-dihydropyridine 5c (O) and its products, monopiva blood () following administration of testosterone, per lyl-dihydro derivative 11 (v), the dihydrodopamine Se. derivative 5a (A) and the quaternary dopamine precur sor 6a (O) in 20% brain homogenate; 65 DETAILED DESCRIPTION OF THE FIG. 4 is a graph plotting the time course of 1-meth INVENTION yl-3-(N-A-(3,4-dipivalyloxyphenyl)ethyl)-carbamoyl More particularly in accord with the present inven 1,4-dihydroxypyridine 5c (O) and its product, the qua tion, the following definitions are applicable: 4,540,564 11 12 The term “lipoidal' as used herein is intended to When the acyl group is designate a carrier moiety which is lipid-soluble or lipophilic. O The expression "hydroxyl protective group' is in | tended to designate a group which prevents premature phenyl-CH2-C- metabolism of an OH group or groups prior to the con pound's reaching the desired site in the body. Typical there are included, for example, benzoyl, phenylacetyl, hydroxyl protective groups contemplated by the pres a-phenylpropionyl, g-phenylpropionyl, p-toluyl, m-tol ent invention (e.g., for Y in the case of the dopamine uyl, o-toluyl, o-ethylbenzoyl, p-tert-butylbenzoyl, 3,4- derivatives) are acyl groups and carbonates. O dimethylbenzoyl, 2-methyl-4-ethylbenzoyl, 2,4,6- When the hydroxyl protective group is acyl (i.e., trimethylbenzoyl, m-methylphenylacetyl, p-isobutyl when it is an organic radical derived from a carboxylic phenylacetyl, (3-(p-ethylphenyl)-propionyl, p-anisoyl, acid by removal of the hydroxyl group), it preferably m-anisoyl, o-anisoyl, m-isopropoxybenzoyl, p-methoxy represents an acyl radical selected from the group con phenylacetyl, m-isobutoxyphenylacetyl, m-die 15 thylaminobenzoyl, 3-methoxy-4-ethoxybenzoyl, 3,4,5- sisting of alkanoyl having 2 to 8 carbon atoms; alkenoyl trimethoxybenzoyl, p-dibutylaminobenzoyl, p-n- having one or two double bonds and 3 to 8 carbon butoxybenzoyl, 2,4,6-triethoxybenzoyl, 3,4-diethoxy atoms; phenylacetyl, R-(3,4,5-trimethoxyphenyl)propionyl, O o-iodobenzoyl, m-bromobenzoyl, p-chlorobenzoyl, p I 20 fluorobenzoyl, 2-bromo-4-chlorobenzoyl, 2,4,6-tri cycloalkyl-CH2-C- chlorobenzoyl, p-chlorophenylacetyl, a-(m-bromo phenyl)propionyl, p-trifluoromethylbenzoyl, 2,4-di(tri wherein the cycloalkyl portion contains 3 to 7 ring fluoromethyl)benzoyl, m-trifluoromethylphenylacetyl, atoms and n is zero, one, two or three; phenoxyacetyl; g-(p-trifluoromethylphenyl)propionyl, 2-methyl-4- pyridinecarbonyl; and 25 methoxybenzoyl, 3-chloro-4-ethoxybenzoyl, g-(3-meth yl-4-chlorophenyl)propionyl, p-dimethylaminobenzoyl, O p-(N-methyl-N-ethylamino)benzoyl, o-acetamidobenz oyl, m-propionamidobenzoyl, 3-chloro-4-acetamido phenyl-CH2-C- phenylacetyl and p-acetamidophenylpropionyl. 30 wherein n is zero, one, two or three and phenyl is un When the hydroxyl protective group is a carbonate substituted or is substituted by 1 to 3 alkyl each having grouping, it has the structural formula 1 to 4 carbon atoms, alkoxy having 1 to 4 carbon atoms, halo, trifluoromethyl, dialkylamino having 2 to 8 car bon atoms or alkanoylamino having 2 to 6 carbon 35 atOnS. When the acyl group is alkanoyl, there are included i.e., it is an organic radical which can be considered to both unbranched and branched alkanoyl, for example, be derived from a carbonic acid by removal of the hy acetyl, propionyl, butyryl, isobutyryl, valleryl, isovale droxyl group from the COOH portion. Y' preferably ryl, 2-methylbutanoyl, pivalyl (pivaloyl), 3-methylpen represents alkyl having 1 to 7 carbon atoms; alkenyl tanoyl, 3,3-dimethylbutanoyl, 2,2-dimethylpentanoyl having one or two double bonds and 2 to 7 carbon and the like. Pivalyl and isobutyryl are especially pre atoms; ferred. When the acyl group is alkenoyl, there are included, cycloalkyl-CnH2n for example, crotonyl, 2,5-hexadienoyl and 3,6-octadi 45 enoyl. wherein the cycloalkyl portion contains 3 to 7 ring When the acyl group is atoms and n is zero, one, two or three; phenoxy; 2-, 3- or 4-pyridyl; or O 50 phenyl-CnH2n cycloalkyl-CH2-C- wherein n is zero, one, two or three and phenyl is un there are included cycloalkanecarbonyl and cycloalk substituted or is substituted by 1 to 3 alkyl each having anealkanoyl groups wherein the cycloalkane portion 1 to 4 carbon atoms, alkoxy having 1 to 4 carbon atoms, can optionally bear 1 or 2 alkyl groups as substituents, 55 halo, trifluoromethyl, dialkylamino having 2 to 8 car e.g. cyclopropanecarbonyl, 1-methylcyclopropanecar bon atoms or alkanoylamino having 2 to 6 carbon bonyl, cyclopropaneacetyl, a-methylcyclopropanea atoms. Most preferably, Y" is C1-C7 alkyl, particularly cetyl, 1-methylcyclopropaneacetyl, cyclopropanepro ethyl or isopropyl. pionyl, a-methylcyclopropanepropionyl, 2-isobutylcy Similarly, the expression "carboxyl protective clopropanepropionyl, cyclobutanecarbonyl, 3,3-dime 60 group' is intended to designate a group which prevents thylcyclobutanecarbonyl, cyclobutaneacetyl, 2,2- premature metabolism of a COOH group or groups dimethyl-3-ethylcyclobutaneacetyl, cyclopentanecar prior to the compound's reaching the desired site in the bonyl, cyclohexaneacetyl, cycloheptanecarbonyl and body. Typical carboxyl protecting groups are the cycloheptanepropionyl. groups encompassed by Y above, especially C1-C7 When the acyl group is pyridinecarbonyl, there are 65 alkyl, particularly ethyl or isopropyl. included picolinoyl (2-pyridinecarbonyl), nicotinoyl By "centrally acting' drug species, active agent or (3-pyridinecarbonyl) and isonicotinoyl (4-pyridinecar compound as utilized herein, there is of course intended bonyl). any drug species or the like, the principal pharmacolog 4,540,564 13 14 ical activity of which is CNS and a result of direct a sedative, trihexyphenidyl, a centrally acting anticho action in the brain. linergic; hydroxyzine, a tranquilizer; chlortetracycline, Exemplary such centrally acting drug species are the demeciocycline, minocycline, doxycycline, oxytetracy CNS-amines and other nervous system agents, whether cline, tetracycline and methacycline, which are tetracy sympathetic or parasympathetic, e.g., phenylethyla- 5 cline-type antibiotics; clindamycin, lincomycin, nali mine, dopamine, tyramine, L-DOPA, muscle relaxants, dixic acid, oxolinic acid and phenazopyridine, antibac tranquilizers and antidepressants, e.g., benzodiazepine terials/antibiotics; flurazepam, bromazepam and loraze tranquilizers such as diazepam and oxazepam, phenothi pam, tranquilizers; phenytoin, an anticonvulsant; glu azine tranquilizers such as carphenazine, fluphenazine tethimide, a mild hypnotic/sedative; bethanidine and and the like, mild and strong analgesics and narcotics, 10 guanethidine, hypotensives/sympatholytics; captopril; sedatives and hypnotics, narcotic antagonists, vascular methyprylon; propranolol, a 6-blocker antihyperten agents, stimulants, anesthetics, small peptides, such as sive; dicloxacillin, an antibacterial; butalbital, a barbitu the di, tri-, tetra- and pentapeptides, and other small rate sedative; GABA, y-vinyl GABA, y-acetylenic 6-20 aminoacid unit containing peptides, e.g., the enke GABA, neurotransmitters for possible use in epilepsy; phalins (for example, Tyr-Gly-Gly-Phe-Leu), which, 15 valproic acid and its metabolites such as 5-hydroxy-2-n- besides being analgesics, initiate epileptic activity in the propylpentanoic acid, 4-hydroxy-2-n-propylpentanoic brain at doses that are about tenfold lower than for acid, 3-hydroxy-2-n-propylpentanoic acid, for use as effecting analgesic activity, larger peptides, such as anticonvulsants; apomorphine, a narcotic depressant/e- pituitary hormones and related agents, antiepileptic and metic; pholcodine, a narcotic antitussive; methotrexate, anticonvulsant drugs generally, including hydantoins 20 podophyllotoxin derivatives (etoposide, teniposide), such as phenytoin and ethotoin, barbituates such as doxorubicin, daunamycin and cyclophosphamide, an phenobarbital, hormones, such as the steroid hormones, ticancer/antitumor agents; methylphenidate, a stimu e.g., estradiol, testosterone, 17 a-ethynyl testosterone, lant; thiopental, an anesthetic; ethinyl estradiol and and the like (recent studies on histological mapping of mestranol, estrogens; meptazinol, cyclazocine, phenaz hormone-sensitive and specific steroid binding cells in 25 ocine, profadol, metopon, drocone and myfadol, which the brain have underscored the importance of the ste are narcotic analgesics; buprenorphine, nalbuphine, roid action in the brain on sexual behavior), ampheta butrophanol, levallorphan, naltrexone, alazocine, oxil mine-like drugs, anticancer and anti-Parkinsonism orphan and nalmexone, which are narcotic antagonists agents, antihypertensives, agents to enhance learning or agonist-antagonists; norgestrel and norethindrone, capacity and the memory processes, including treat- 30 progestins; cephalothin, cephalexin, cefazolin and ment of dementias, such as Alzheimer's disease, antibac cefoxitin, cephalosporin antibiotics; atenolol and meto terials, centrally active hypotensive agents, diagnostic prolol, 9-blockers/hypotensives; ACTH (corticotro agents, such as radiopharmaceuticals, monoamine oxi pin); LH-RH, a neurotransmitter; sulfadiazine and other dase (MAO) inhibitor drugs, CNS or brain impor sulfonamide antibiotics; ribavirin and acyclovir, antivi tant/essential amino acids, such as tryptophan, and any 35 ral agents; chlorambucil and melphalan, nitrogen mus like centrally acting compounds. tard-type anticancer/antitumor agents; methotrexate Other illustrative ultimate species of centrally active and aminopterin, which are folic acid antagonist-type drug entities are: amphetamine, dextroamphetamine, anticancer/antitumor agents; platinum coordination levamphetamine, methamphetamine, phenmetrazine complexes, i.e. cisplatin analogue-type anticancer/an and phentermine, which are stimulants and appetite 40 titumor agents; dactinomycin and mitomycin C, used in Suppressants; codeine, oxycodone, pentazocine, anilleri cancer chemotherapy; thioguanine, a purine/pyrimi dine, hydromorphone, morphine and oxymorphone, dine antagonist used in cancer treatment; Vincristine and which are narcotic analgesics; desipramine, nortripty vinblastine, anticancer alkaloids; hydroxyurea and line, opipramol and protriptyline, which are stimulants DON, anticancer urea derivatives; FSH and HCS, pitu used, e.g., in endogenous depressions; clonidine and 45 itary and nonpituitary gonadotropins; N,N'-bis(di methyldopa, which are sympatholytic agents used, e.g., chloracetyl)-1,8-octamethylene diamine, an agent for in hypertension; biperiden, cycrimine and procyclidine, male fertility inhibition; levorphanol, a narcotic analge which are centrally acting anticholinergics; tranylcy sic; benzestrol and diethylstilbestrol, synthetic estro promine, a sympathomimetic stimulant and MAO inhib gens; ethyl g-carboline-3-carboxylate, a benzodiazepine itor; acetophenazine, carphenazine, fluphenazine, per- 50 antagonist; furosemide, a diuretic/antihypertensive; and phenazine and piperacetazine, which are phenothiazine dipyridamole and nifedipine, coronary vasodilators. Yet type tranquilizers; chlordiazepoxide, clorazepate, ni other ultimate species include non-steroidal anti-inflam trazepam and temazepam, which are benzodiazepine matory agents/non-narcotic analgesics, e.g. propionic type tranquilizers; haloperidol and clopenthixol, which acid derivatives such as ibuprofen, naproxen, flurbi are tranquilizers; norepinephrine, a sympathetic stimu- 55 profen, fenbufen, fenoprofen, indoprofen, ketoprofen, lant/adrenergic agent; nalorphine and naloxone, nar fluprofen and bucloxic acid; acetic acid derivatives such cotic antagonists; hydralazine, a hypotensive; ethotoin, as indomethacin, Zomepirac, tolmetin, sulindac, di phenobarbital and aminoglutethimide, anticonvulsants; clofenac, alclofenac, fenclozic acid and ibufenac; fe ethamivan, a medullary stimulant; benegride, a barbitu namic acid derivatives such as mefenamic acid, me rate antagonist; amiphenazole, a stimulant; iopydol, 60 clofenamic acid and flufenamic acid; and biphenylcar iodopyracet, iodouppurate, iodamide and iopanoic acid, boxylic acid derivatives such as diflunisal and flufenisal. which are radiodiagnostics; ephedrine, pseudoephed Preferred classes of centrally acting drugs for use rine, oxymetazoline and phenylephrine, which are sym herein are the central neurotransmitters, steroids, anti pathomimetic amines and decongestants; estradiol, es cancer and antitumor agents, antiviral agents, tranquil trone and estriol, the natural estrogens; amoxicillin, 65 izers, memory enhancers and hypotensives. Among the oxacillin, carbenicillin, benzylpenicillin, phenoxyme neurotransmitters, there can be mentioned amino acids, thylpenicillin, methicillin, nafcillin, ticarcillin and ampi such as GABA, GABA derivatives and other omega cillin, which are penicillin-type antibiotics; amobarbital, amino acids, as well as glycine, glutamic acid, aspartic 4,540,564 15 16 acid and other natural amino acids; catecholamines, phenazine, fluphenazine, perphenazine and piperaceta such as dopamine, norepinephrine and epinephrine; zine; and others. Among the hypotensives, there can be serotonin and tryptamine; and peptides such as neuro mentioned clonidine, methyldopa, bethanidine, de tensin, luteinizing hormone-releasing hormone brisoquin, hydralazine, and guanethidine and its ana (LHRH), somatostatin, enkephalins such as met-enke- 5 logues. phalin and leu-enkephalin, endorphins such as y-, a and 6-endorphins, oxytocin M and vasopressin. Syn It too will be appreciated that by "dihydropyridine thetic and semi-synthetic analogues, e.g. analogues of carrier' or "DHC', there is intended any nontoxic LHRH in which one or more amino acid(s) has/have carrier moiety comprising, containing or including the been replaced with one or more different amino acid(s), 10 dihydropyridine nucleus, whether or not a part of any and which may be agonists or antagonists, are also con larger basic nucleus, and whether substituted or unsub templated. Among the steriods, there can be mentioned stituted, the only criterion therefor being capacity for antiinflammatory adrenal cortical steroids such as hy BBB penetration and in vivo oxidation thereof to the drocortisone, betamethasone, cortisone, dexametha corresponding quaternary pyridinium salt carrier sone, flumethasone, fluprednisolone, meprednisone, 15 QC+. As aforesaid, the ionic pyridinium salt drug/- methyl prednisolone, prednisolone, prednisone, triam carrier prodrug entity (D-QC) which results from cinolone, cortodoxone, fludrocortisone, flurandreno such in vivo oxidation is prevented from efflux from the lone acetonide, paramethasone and the like; male sex brain, while elimination from the general circulation is hormones (androgens), such as testosterone and its close accelerated. Subsequently, the covalent or equivalent analogues, e.g. methyl testosterone; and female sex hor- 20 bond coupling the drup species D) to the quaternary mones, both estrogens and progestins, e.g., ethinyl es carrier QC is metabolically cleaved which results in tradiol, norgestrel, mestranol, norethindrone, nore sustained delivery of the drug (D) in the brain and facile thynodrel, ethisterone, estradiol, estriol, estrone, dime elimination of the carrier moiety QC. Such "cova thisterone, allylestrenol, cingestol, ethynerone, lynes lent or equivalent bond' between the drug and the trenol, norgesterone, norvinisterone, ethynodiol, ox- 25 ogestone, tigestol, quinestrol and the like. Among the quaternary carrier can be a simple direct chemical bond, anticancer and antitumor agents, there can be men e.g., an amide, an ester, or any other like bond, or same tioned Ara-AC, pentostatin(2'-deoxycoformycin), Ara can even be comprised of a linking group or function, C, 3-deazaguanine, dihydro-5-azacytidine, tiazofurin, e.g., a thiazolidine bridge or a peptide linkage, typically sangivamycin, Ara-A, 6-MMPR, PCNU, spiromustine, 30 necessitated when the drug species is not susceptible to bisbenzimidazole, L-alanosine, DON, L-ICRF, tri direct chemical coupling to either the dihydropyridine methyl TMM, 5-methyl tetrahydrohomofolic acid, gly carrier or the quaternary carrier. Nonetheless, the bond oxylic acid sulfonylhydrazone, DACH, SR-2555, SR in the formulae (D-QC and D-DHC) is intended to 2508, desmethylmisonidazole, mitoxantrone, menoga be, and is hereby defined as inclusive of all such alterna rol, aclacinomycin A, phyllanthoside, bactobolin, 35 tives. And the cleavage of the D-QC prodrug to aphidocolin, homoharringtonine, levonantradiol, acivi sustainedly delivery the drug species (D) in the brain cin, streptozotocin, hydroxyurea, chlorambucil, cyclo with concomitant facile elimination of the carrier moi phosphamide, uracil mustard, melphalan, 5-FUDR, ety (QC) is characteristically enzymatic cleave, e.g., Vincristine, vinblastine, cytosine arabinoside, 6-mercap by esterase, amidase, cholinesterase, hydrolytic en topurine, thioguanine, 5-azacytidine, methotrexate, 40 zyme, or peptidase, albeit any type of in brain cleavage adriamycin (doxorubicin), daunomycin, largomycine which might result, whether enzymatic, metabolic or polypeptide, aminopterin, dactinomycin, mitomycin C, otherwise, of course remains within the ambit of this and podophyllotoxin derivatives, such as etoposide invention. Thus, the drug release rate controlling pa-. (VP-16) and teniposide. Among the antiviral agents, rameter of the subject pro-prodrugs is imparted simply there can be mentioned ribavirin; acyclovir (ACV); 45 via the cleavable bonding between drug and carrier, amantadine (also of possible value as an anti-Parkinso and not by any release rate controlling substituent(s). nism agent); diarylamidines such as 5-amidino-2-(5- amidino-2-benzofuranyl)indole and 4,6-diimidazolino The expression "non-toxic pharmaceutically accept 2-phenylbenzo(b)thiophene; 2-aminoxazoles such as able salts' as used herein generally includes the non 2-guanidino-4,5-di-n-propyloxazole and 2-guanidino- 50 toxic salts of compounds of formula (I), wherein D is 4,5-diphenyloxazole; benzimidazole analogues such as a centrally acting drug species and DHC is the re the syn and anti isomers of 6(hydroxyimino)phenyl)- duced, biooxidizable, blood-brain barrier penetrating methyl-1-(1-methylethyl)sulfonyl)-1H-benzimidazole form of a dihydropyridine-pyridinium salt redox car 2-amine; bridgehead C-nucleosides such as 5,7-dimeth rier, formed with nontoxic, pharmaceutically accept yl-2-3-D-ribofuranosyl-s-triazole(1,5-a)pyrimidine; 55 able inorganic or organic acids HX. For example, the glycosides such as 2-deoxy-D-glucose, glucosamine, salts include those derived from inorganic acids such as 2-deoxy-2-fluoro-D-mannose and 6-amino-6-deoxy-D- hydrochloric, hydrobromic, sulfuric, sulfamic, phos glucose; phenylglucoside derivatives such as phenyl-6- phoric, nitric and the like; and the salts prepared from chloro-6-deoxy-6-D-glucopyranoside; (S)-9-(2,3-dihy organic acids such as acetic, propionic, succinic, glycol droxypropyl)adenine; 6-azauridine; indoxuridine; 60 lic, Stearic, lactic, malic, tartaric, citric, ascorbic, pa BDVU (bisdihydroxyvinyluridine); and 5,6-dichloro-1- moic, maleic, hydroxymaleic, phenylacetic, glutamic, E-D-ribofuranosylbenzimidazole. Among the tranquil benzoic, salicylic, sulfanilic, fumaric, methanesulfonic, izers, there can be mentioned benzodiazepine tranquiliz toluenesulfonic and the like. ers such as diazepam, oxazepam, lorazepam, chlordiaz In one ambodiment according to this invention, sim epoxide, flurazepam, bromazepam, chlorazepate, ni- 65 ple nontoxic carrier systems (D-QC+-2D-DHC are trazepam and temazepam; hydantoin-type tranquilizers envisaged, utilizing a wide variety of models for D, such as phenytoin, ethotoin, mephenytoin; phenothia such as those above outlined. Representative such car zine-type tranquilizers such as acetophenazine, car rier systems and models are: 4,540,564 17 18 -continued

HO OR3

DZ OH R = -CO O

R3O OR3 -- CH3 O 3

NSs G-con s C-con Yet other redox carriers include those comprising an N N 15 acidic chain directly linked to the heterocyclic nitro R2 gen, in quaternary or tertiary amine form. Also the hydroxide type carriers, e.g., the glucosamine analog wherein R2 is simply alkyl, e.g., CH3, or benzyl, albeit indicated below. Representative are: virtually any other effective substituent is intended. (As depicted above, the isomeric dihydropyridine structure 20 depends on the position of the substituent relative to the COR2 COR1 (a) pyridine nitrogen.) Exemplary of such simple carrier systems are N-alkyl nicotinamide and nicotinate ester derivatives, tethered to such drug species as dopamine, 25 (OsO N N melphalan and testosterone. The trigonelline (N- methylnicotinic acid) system is quite effective as a car k-co-d k-co-d rier; it also is readily eliminated from the circulation and R=NH2; OR2; and the like is virtually non-toxic. 30 Indeed, the present invention provides a flexible arse R2 = alcohol residue nal of dihydropyridine-pyridinium salt redox carriers R3 = (CH2), n = 1-10 or C1-C12 branched alkyl, aryl for the site-specific/sustained delivery of virtually any centrally acting drug species to the brain, Moreover, alkyl, and the like any dihydropyridine/pyridinium salt redox carrier en 35 D= drug-NH2 or -OH; tity is contemplated and intended hereby generically, Preparation: and any such carrier moiety need not be, and is not derivatized with a drug release rate controlling substitu COR COR ent critically tailored to meet, or be coordinated with, 40 the chemical nature and delivery requirements of the particular drug species sought to be preferentially ad (O. H2N-R3-COOR2 - >O6 ministered to the brain. As utilized herein, the term N -- "carrier' is to be understood as connoting just such a NO2C1 R3-COOR2 non-derivatized, non-drug/carrier coordinated entity, 45 for consistent herewith it is the "carrier' entity itself D-OH or DNH2 and not the nature of any activity or release rate con trolling/modifying substituent which is responsible for NO2 providing the desired brain-specific result. 50 COR2 COR1 Additional examples of such redox carriers include the quaternary pyridinium alcohols (1), the analog iso | 11actionreduction O quinoline acid and alcohol systems (2), and multi charged delivery forms, exemplified by structure 3 (D N. represents drug, Z, a covalent link) and obviously the 55 R3-COD R3-COD corresponding dihydro forms. Method of: H. Lattreet al., Annalem, 579, 123 (1953).

60 R2 CH-Z-D C-Z-d N COR COR (b) N: + n R1 R R2 s 2 65 N N X = H2 or O k-co-D k-co-D 4,540,564 19 20 -continued -continued CH2OH CH2OH (c) (vi) OoH 9 oH 5 Cam-D OH DNPNS OH O HO HO N

Y 1. COR -- NH2 1 COR1/ R 1. -- A. --- 1 N 10 O s L-N in which R1 is defined as above; and (d) the quinolinium and isoquinolinium systems Generally preferred dihydropyridine-pyridinium salt redox carriers for use in the present invention in 15 CONH2 (vii) clude the following (where D represents the drug), and O and obviously the corresponding dihydro forms: N. (a) the pyridinium systems R3-CO-D 20 (i) CONH2 (viii) 25 O. R3-Co-D R1 in which R3 is defined as above. The corresponding O (ii) dihydro forms of the foregoing preferred pyridinium CH2C-D and 30 salts are depicted below, wherein the position and iden tity of the structural variables are as indicated above: R1 O (i) 35 O (iii) CH2-OC-D r 40 N R in which the depicted substituent is in the 2-, 3- or 4 position, and R1 is C1-C7 alkyl or C7-C10 aralkyl, pref (ii) erably methyl or benzyl; 45 CH2C-D, (b) the pyridinium system

(iv) N 50 R

N. (iii) R3-CO-D CH-OC-D, in which R3 is C1 to C3 alkylene, i.e., (CH2) where n = 1-3; 55 5 (c) the isoquinolinium and quinolinium systems 60 RN O (v) C-D r" (iv) O and 65 Nts R2 4,540,564 21 22 -continued the dihydro form to the quaternary (K3 and K7) and the O (v) rates of its disappearance from the brain (K4--K5). At the same time, the very water soluble quaternary C-D form(s) 6 is/are excreted readily via the kidney and the N 5 liver (K8) > K4). Derivatives 6 are considered to be essentially inactive forms (K8) > K9), and thus sys N temic activity/toxicity is minimized. Hence, the con n R1, centration of 5 and 6 in the blood rapidly increases. The ratio of the quaternary salt 6 in the brain relative to the (vi) 10 blood increases to the point where 6, or metabolites C-D, thereof, can only be found in the brain. The quaternary 6, whether in the brain, blood or other tissues, is deemed to release dopamine and the non-toxic compound, trigo N nelline, depending upon the rates of site-specific con 15 version of the precursor 6 to the drug at each of these R sites. The concentration of any released dopamine at any time is much higher in the brain than in the blood or CONH2 (vii) other tissues. Also, as the enzymatic transformation of the quaternary precursor 6 to the drug (dopamine) is 20 relatively slow, same permits a sustained release of do N pamine. Too, the simultaneous protection/lipophilic R3-CO-D, derivatization of the catechol system in dopamine has also now been demonstrated. CONH2 (viii) It will be appreciated that a compound of formula (I), 25 such as compound 5, may be administered as depicted in N Scheme 3, or in the form of a non-toxic pharmaceuti cally acceptable salt thereof, i.e., a salt which can be N R3-CO-D. represented by the formula In a preferred embodiment of the present invention, 30 sustained delivery of drug to the brain in pharmacologi OR cally effective concentrations has now been demon HX strated, paralleled with much lower concentrations in N OR the peripheral circulation and other tissues, utilizing dopamine as the target drug species and a trigonelline 35 | | H| type carrier system, with the catechol moiety thereof in N certain instances being acylated, e.g., acetylated or (R is defined as in pivalylated. According to Scheme 3 which follows, one CH3 Scheme 3) specific delivery system for dopamine, compound 5, on 40 wherein HX is as defined before; and that, regardless of administration (e.g., by injection) is distributed through the actual form in which the compound is administered, out the body and by reason of its lipophilic character it will be converted in vivo to a quaternary salt of the facilely penetrates the blood-brain barrier and enters the compound 6 type, the anion X being an anion present CNS. Following oxidation both in the brain and in the in vivo. It is not necessary that the compound 6 anion be other tissues, the corresponding hydrophilic quaternary introduced as part of the compound 5. And even when salt (6) is formed. The quaternary salt 6 is essentially 45 the compound 5 is used in its salt form, the anion of 6 is "locked in' the brain and its concentration is considered not necessarily the same as that present in compound 5. to increase with time until reaching a maximum, which In any event, the exact identity of the anionic portion of depends primarily on the relative rates of entrance of the compound 6 is immaterial to the depicted enzymatic the dihydro compound (5) to the brain (K1) as com transformation. pared to K2 to the other tissues, the rate of oxidation of

Scheme 3: OR

OR

5 4,540,564 23 24 -continued Scheme 3: R = H (a), COCH3(b) COC(CH3)3 (c)

administration Other tissues K2 K. Brain Distribution

K7, oxidation oxidation , K3

oR BBB OR O O

N OR N OR H O H N: CH3X 6 (a-c) CH3X 6(a-c) K4 K5 -1 421 K8 K9 Depamine Excretion Dopamine K6 K + -- O Excretion Trigonelline Trigonelline

Excretion, Metabolism Excretion,y Metabolism With specific reference to the immediately above, the 1,4-dihydropyridine derivatives (5) were prepared as in the following Scheme 4:

Scheme 4: O I OH O OH N O OH -- pyridine G N OH DCC H Br-H3N+ OH N 7

RCI or other acyl halide

OR OR O C CH3I O N OR N OR O H N-- N C H 3 8 reduction 4,540,564 25 26 -continued Scheme 4: OR O

N OR

CH3 s

15 The stability of the 1,4-dihydropyridine derivatives R=H (a), COCH3(b), COC(CH3)3 (c) (5) was determined in the presence of the oxidizing DCC= dicyclohexylcarbodiimide agents, alcoholic AgNO3 and hydrogen peroxide. The Similar schemes can be shown for the preparation of 20 in vitro rates of oxidation of the 1,4-dihydropyridine the other dopamine derivatives of the invention. The derivative (5c) in 80% plasma, 20% brain homogenate, step which introduces the protecting groups is of course 20% liver homogenate and in whole blood were deter only required when it is desired to protect the catechol mined. hydroxyl groups. Moreover, when carbonate rather The dihydropyridine derivative (5c) was then se than acyl protecting groups are desired, the step of 25 lected for the in vivo study. A solution in DMSO (di introducing the protecting groups will involve reacting methylsulfoxide) was injected through the jugular vein the catechol with a halocarbonate of the type Y'OCOCl to a group of male Sprague-Dawley rats which were or Y'OCOBr (formed by reaction of Y'OH with COCl2 then sacrificed at various time intervals; their blood and or COBr2), rather than with an acyl halide YC1 or YBr, brains were analyzed for the quaternary precursor of Y and Y being as generically defined hereinabove. 30 dopamine (6a). The in vivo dopaminergic activities of Also, the order of steps shown in Scheme 4 may be the selected compounds 5c vs. 6a were then determined. altered; quaternization, followed by reduction, need not Consistent with the above, it was found that N be in the final two steps but may be carried out earlier nicotinoyldopamine (7) could be obtained in good in the reaction sequence. Yet other reaction schemes yields by coupling dopamine hydrobromide with nico and reactants (e.g., using an anhydride rather than an 35 tinic acid in pyridine as a solvent and with dicyclohex acyl halide to convert 7 to 8) will be readily apparent to ylcarbodiimide as the coupling agent. Attempts to pre those skilled in the art, Scheme 4 being simply a pre pare 7 by using dopamine free base were largely unsuc ferred approach for the specific compounds there de cessful. As for the catechol protecting groups, the ace picted. Variations of this approach are likewise applica tyl and pivalyl moieties were selected due to their ble to preparing derivatives of other hydroxy-contain rather different steric and partitioning parameters. Acy ing amines. lation could be accomplished with the acyl chlorides by In an attempt to ascertain whether any biotransfor using conventional methods. Reduction of the quaterna mation of the free catechol is taking place by COMT ries (6a-c and 9) was accomplished by using sodium (catechol-O-methyltransferase) either before or after dithionite in mildly basic aqueous solution, (NaHCO3). oxidation, the possible O-methyl metabolites (9 and 10) 45 It was observed that the dihydro compound obtained in were synthesized separately following Scheme 4 with the case of the quaternary 6b gave a faint green color 3-methoxytyramine hydrochloride as the starting mate with ferric ions, indicating partial hydrolysis of at least rial. one of the acetyl moieties during reduction, even in the cold, weakly basic solution used as a medium. The dihy 50 dropyridine derivatives isolated (5a-c and 10) were OH determined to have the expected 1,4-dihydropyridine O structure, based on their NMR and UV spectra. At l tempts to prepare the g-protonated enamine salts of the N OCH3 isolated dihydro derivatives were also largely unsuc 55 cessful, due to acid catalyzed addition reactions. The O 1,4-dihydropyridine derivatives (5a-c) were found to be N. 9 relatively stable towards oxidation. Compound 5c was CH3 I quantitatively oxidized to the corresponding quaternary salt 6c by H2O2 or alcoholic AgNO3 solution. OH The diacetyl derivatives (5b and 6b) appeared to be O labile to hydrolysis and therefore were not pursued in vitro. The dipivalyldihydro derivative (5c) was thor N OCH3 oughly investigated for its in vitro rates of disappear ance and metabolic degradation in various biological 10 65 fluids. It is evident that 5c represents a rather complex case, as besides oxidation, a two-step hydrolysis will CH3 also take place. Scheme 5 illustrates the interconversion of the possible components. 4,540,564 27 28

Scheme 5:

O

N H N CH3 4, CoH N 11 CH3

OH O

N OH

N 5a CH3 C OH (Ori OH CH3 FIGS. 1-4 illustrate the results of such an investiga tion. The apparent half-lives for the disappearance of 5c sion routes and it is the direct precursor thus concluded in biological fluids at 37 C. were calculated. Although 50 to be locked in the brain in the in vivo experiment. No the process does not truly follow first order kinetics, the formation of the methoxy derivatives 9 and 10 could be data fit very closely a pseudo first order process (FIG. detected in any of the biological fluids studied; 5a and 5). The obtained values, 51 min (80% plasma), 17 min 6a does not appear to be good substrates for COMT. (20% brain homogenate), 18 min (whole citrated blood) The first objective of the in vivo studies was to trace and 6 min (20% liver homogenate), reflect an accept 55 the appearance and disappearance of 6a in blood and able stability of the dihydro derivative 5c. The disap brain following administration of 5c. FIG. 6 summarizes pearance of 5c is accompanied by formation of some such results, and is consistent with the mechanism monoester (11) and dihydroxy dihydro form (5a) in all shown in Scheme 3. After one single injection of the the media except the liver homogenate. The rate of 1,4-dihydropyridine derivative 5c to the rat, the dihy hydrolysis of the first ester moiety is faster than the 60 droxy quaternary 6a (ion), which is the only detectable second and a reasonable amount of monoester l l builds derivative, could be seen to appear and then to disap up with time. The monohydroxy quaternary 12 could pear quickly from the blood, with a half-life of 27 min. not be detected except in the blood as a very small peak On the contrary, the concentration of 6a (ion) is increas which does not change significantly with time. A steady ing in the brain steadily, reaching a maximum at about increase in the concentration of the dihydroxy quater 65 30 min following administration. The descending por nary 6a was observed in all media except liver homoge tion indicates a half-life of disappearance from the brain nate. Thus, it is established that this derivative, 6a, is of about 3.2 h. No formation of O-methyl metabolites forming as the main product of the various interconver (9, 10) could be detected in the brain. This confirms the 4,540,564 29 30 in vitro results that 6a (or 5a) is not a good substrate for significantly lower effect of 6a when administered I.V. COMT. does not unequivocally clarify which alternative is the To determine whether dopamine itself was finally more responsible. This was resolved by in vitro com released in the brain upon completion of the aforesaid parison of the relative activities of dopamine versus 6a. complex delivery process, 5c was administered in Fresh anterior pituitaries obtained from female rats trajugularly and changes in brain-dopamine concentra were incubated with various concentrations of dopa tions following that administration were studied. Some mine (DA) and 6a, respectively, and their effects on the of the rats showed up to threefold increase in the dopa rate of release of prolactin were measured. It was found mine concentrations, others practically none. Since it is that at 2x 108M concentrations, neither DA nor 6a possible (and even desired) that the intrinsic brain me 10 had any effect, but at 2x 107M, DA caused a 57% tabolism of the dopamine does not permit significant reduction of the prolactin rate secretion, while 6a had build-up of its concentration, specific pharmacologic no effect. These results are summarized in the following activity was investigated, using changes in the in vivo Table I.

TABLE I Comparative in vitro activity of 6a vs. dopamine Prolactin ng/mg/h? Dopamine (DA)* 6ad DA DA 6a 6a control 2 x 108M control 2 x 107M control 2 x 10-8M control 2 x 10x7M 344 - 50 355 67 282 34 12 - 38 342 - 38 386 29 250 - 30 277 - 32 On freshly obtained anterior pituitary (AP) at 37 C. All values are average of 9 separate AP-S. Prolactin release rate of the incubated AP-S. Weight of the AP-S: control 4.6 - 0.2 mg. DA treated 4.5 - 0.3 mg. Weight of the AP-S: control 4.6 t 0.3 6a treated 4.7 + 0.4 *P & 0.05 polactin secretion. It is known that dopamine and its These results indicate that if 6a has any activity, it agonists decrease prolactin secretion following their must be significantly less than that of DA. Based on the binding to stereospecific receptors located on lacto 40 delayed onset of the activity when 6a was administered phors in the anterior pituitary (AP) gland G. P. Muel I.V. and considering the in vitro results, it logically ler, J. W. Simpkins, J. Meites and K. E. Moore, Neuro follows that the high and prolonged activity of the 6a endocrinology, 20, 121 (1976); W. Wuttke, E. Cassell and locked in the brain following administration of 5c is due J. Meites, Endocrinology, 88, 737 (1971); J. A. Clemens, to the fact that 6a is slowly releasing the active DA in E. B. Smallstig and C.J. Shaar, Acta Endocrinol, 79, 230 45 the brain. (1975). This effect is dose-dependent and it can also be Accordingly, provided hereby is a potent, brain observed in vitro, incubating anterior pituitaries with specific dopaminergic agent comprising a lipophilic dopamine or its agonists R. M. MacLeod in "Frontiers dihydropyridine carrier-type chemical delivery system in Neuroendocrinology", Ed. L. Martini and W. F. of dopamine "pro-prodrug' or "pro-pro-prodrug' in Ganong, Raven Press). 50 the case of the catechol protective group(s)), which It was then determined that exposure of male rats to penetrates the BBB by passive transport. The rapid 17-g-estradiol for two days elevated serum prolactin oxidation in the brain of the carrier moiety to the corre levels to greater than 150 ng/ml. Intravenous adminis sponding quaternary pyridinium salt results in an acti tration of 5c caused a 79% decrease in serum prolactin vated amide of dopamine. The oxidation process is concentrations and this dramatic reduction was main 55 much faster than amide cleavage of the beginning com tained through 120 min after treatment. In contrast, 6a pound 5 or of 6. Moreover, the ionic nature of the acti had no significant effect on the serum prolactin concen vated quaternary salt results in a significant slowdown trations by 15 min, and caused a 67% reduction by 30 of the efflux of this specific form through the BBB, min. Thereafter, serum prolactin levels increased pro resulting in a selective concentration enhancement of gressively to levels which are not significantly different the precursor 6a in the brain. Too, brain-specific from vehicle injected controls, by 60 and 120 min. dopaminergic activity is assured, logically as dopamine These results are summarized in FIG. 7. The rapid onset is released from this activated form upon hydrolytic, and prolonged inhibitory effects of 5c on prolactin se enzymatic or metabolic cleavage, as is facile excretion cretion is consistent with the time course of the appear of the carrier moiety from the brain. ance of 6a in the brain following administration of 5c. 65 In yet another embodiment of the invention, like The "trapping' of 6a in the brain subsequent to I.V. synthesis of the analogous tyramine system has been injection of 5c provides a constant source of a potent carried out, and the corresponding determinations dopaminergic agent, either dopamine or 6a itself. The made. Such tyramine system is represented as follows: 4,540,564 31 32

OR1 O

O?O H N th; IX a-c R = H-(a) CH3CO-(b) (CH3)3CCO-(c) prepared, quaternizing same with methyl iodide to form Naturally, selection of the particular dihy- is dropyridine-pyridinium salt redox carrier to be used will depend on the chemical structure of the specific O drug involved. And not only should the nature of the functional group which is to be linked to the carrier NH-C O I system be considered in selecting the carrier, but the 20 N-CH manner in which the ultimate compound is prepared 3 should be tailored to the presence of any other reactive CH2CH2Cl groups in the molecule. The following examples of H5COOC-CH-CH2 N specific drug/carrier combinations and their manner of N synthesis are set forth for the purpose of illustration 25 CH2CH2Cl, only and are not to be considered limitative in any way whatsoever. which can then be reduced to afford the melphalan Thus, in one specific illustration, the selected drug is CDS testosterone and the selected carrier system is trigonel line edihydrotrigonelline; according to this embodi- so ment, testosterone is reacted with nicotinoyl chloride, \ the resultant ester is then quaternized with methyl io- NH-C dide, and the quaternary iodide is then reduced with \ Na2S2O4 to afford the testosterone-CDS (chemical de- N-CH3 livery system) 35 CH2CH2Cl

O N I cock-a-O)-x CH2CH2Cl. O 40. As one of several alternative schemes, melphalan can be N derivatized by first esterifying it, e.g., to convert the carboxy function to the ethyl ester, then reacting the CH3. resultant melphalan ethyl ester with nicotinoyl chloride to form the amide of the formula 45 O O Other steroids can be similarly derivatized, e.g., 17a NH-C ethynyltestosterone, estradiol and the like. Another specific illustration involves selecting mel N phalan and the same type of carrier system as above, but CH2CH2Cl forming an amide rather than an ester linkage. Thus, / melphalan is converted to its hydrobromide, which is H5C2OOC-CH-CH2 N reacted with nicotinic acid to afford the amide having CH2CH2Cl, the formula 55 which can then be quaternized and the quaternary salt subsequently reduced as indicated above to afford to O same melphalan-CDS as depicted above. NH-C Yet another specific illustration utilizes chlorambucil 60 as the target drug, in which case the desired nicotinic N acid carrier system is linked to the drug via a bridging CH2CH2C) / group. Thus, nicotinic acid can be reacted with an ap HOOC-CH-CH2 N propriate di- or polyhydroxy compound such as ethyl N ene glycol, propylene glycol or inositol and the resul CH2CH2Cl, 65 tant intermediate is linked via its free hydroxy group(s) to the carboxylic acid function of chlorambucil. That which can be esterified, if desired (to increase lipoidal intermediate is then quaternized and the quaternary salt characteristics), followed by, when the ethyl ester is is reduced to afford the chlorambucil-CDS. In the case 4,540,564 33 34 of nicotinic acid and ethylene glycol starting materials, can be derivatized similarly to chlorambucil via its car the chlorambucil-CDS has the formula boxy function(s), e.g., utilizing the inositol trigonelli 5 nates or a glucosamine analogue. O O CH2CH2Cl As a further example, podophyllotoxin and its deriva / / / 8-OCHCHyocho-O- N tives can be linked to a carrier system of this invention. N CH2CH2Cl. These drugs can be represented by the structual formula 10 CH3 On the other hand, when a polyhydroxy compound is reacted with nicotinic acid in the first step, a variety of 15 S products are possible. Thus, for example, when inositol is used, the final product may contain anywhere from 1 carrier/5 drug residues to 5 carrier/1 drug residue. In E the case of the inositol trinicotinate intermediate 20

CH3O OCH3 OR5 25 R5 = H or CH3 R4 = OH-podophyllotoxin

30 O-CH2 / O R4 = CH W conditions for reacting same with chlorambucil can be R6 / Yo OH N selected so that one, two or three of the hydroxy func- 3 tions react with the acid. When all three hydroxys react, OH the ultimate chlorambucil-CDS has the formula R4(R6 = CH3-etoposide 40 S -teniposide)

45 and can be derivatized by reacting the hydroxy group in podophyllotoxin (R4 = OH) or the hydroxy groups in the glycosidic portions in R4 with acidic type redox 50 carriers, e.g., in a manner analogous to the testosterone CDS depicted above. Known cisplatin analogues, in which typically the amino groups have been replaced with organic radicals, can be similarly derivatized ac 55 and contains 3 drug residues and 3 carrier groupings. cording to the invention, the method of choice depend As another example, methotrexate, which has the ing on the nature of the functional groups in the organic structural formula radicals. 60 Similarly, syntheses and like determinations as re COOH CH3 gards the redox carrier-linked enkephalins can be car th 2 -CH NH2 N sa CH2 21 N ried out. First synthesized is the known leucine enke , 65 phalin XI. The quaternary pyridinium analog XII, the SH-NHoc S. N N 2. COOH NH2 corresponding O-benzyl ether XIII and the amide XIV are next synthesized. 4,540,564 35 36

Tyr Gly Gly Phe Leu CONH-CH-CONHCH2CONHCH2CONHCHCONHCH-COOCH5 Tyr-Gly-Gly-Phe-Leu

XI CH3MCH CH3 CH3 OH XII O CONH-CH-CO-Gly-Gly-Phe-Leu-OEt O CO-Tyr-Gly-Gly-Phe-Leu-NH2 4N +N CH3 CH3 XIV OCH2C6H5 XIII

The O-benzyl pentapeptide ethyl ester derivative of XI is synthesized sequentially and then coupled with 2 -continued nicotinic acid, followed by methylation. Alternate 5 XV methods involve introduction of carrier at an earlier stage in the synthesis. The reduction of XII and XIII results in a mixture of products due to the base sensitiv ity of the ester. Likewise prepared are the correspond ing leucinol trigonelline ester XV and its dihydro deriv- 30 ative XVI. CH3 Thus, the site-specific brain delivery of the enkepha I. XV lins for the treatment of epilepsy iss established- consisA. Tyr-Gly-Gly-Phe-NH-CH-CH2-O-C 35 tent with the Scheme 1, as is their analgesic activity. th Similarly, as regards the benzodiazepine tranquiliz / N CIS, C.9. CH3 CH3 N -- 8 CH3

l. Oxazepam: | O H O - )-on-> - N N C e C e C6H5

2. Diazepam: CH3 O / CH3 N-COCH-NH-CO-R

N C 3. C --O 4,540,564 37 38 -continued

(1) delivery (2) oxidation

sustained brain release in vivo

This reaction scheme utilizes conventional opening of 20 with. Model compounds include carboxylic acids, most the 7-member ring, accompanied by coupling of the specifically valproic acid, as well as some of the GABA drug to the carrier. The following drugs can be simi analogs which inhibit irreversibly the GABA-T, such as larly derivatized to the corresponding dihydro deriva y-vinyl and/or y-acetylenic GABA. Using the afore tives: said trigonelline (N-methylnicotinic acid)--dihydro 25 trigonelline system, for example, the selected com pounds can be effectively delivered per Scheme 1. Thus, representative target compounds are the dihydro pyridine carrier-drug combinations 1 and the corre sponding pyridinium carrier-drug species, for example, GABA and its esters:

CONH-CH2CH2CH2COOR2 CONHCH2CH2COOR2 -N S N R la

R2 = H, C2H5, CH(CH3)2, etc. 45 Related derivatives for y-vinyl and y-acetylenic GABA are: flurazepam CH2 Z CH 50

2 and 2a

CH 55 / RNH&HCHCH-coors bromazepam 3 and 3a And in another preferred embodiment of the inven tion, there is provided the effective, selective and non toxic treatment of epilepsy, based upon the mechanism CO- CO illustrated in Scheme 1. Indeed, commencing from the "GABA-hypothesis' of epilepsy, the brain-specific, R3 = O O N N enhanced and sustained release of GABA (y- 65 aminobutyric acid) itself, and various other compounds k k either directly or indirectly affecting the concentrations of GABA in the brain, is circumscribed consistent here In the case of valproic acid, other alternatives are: 4,540,564 39 40

n (n-C3H7)2CHCOO-CH2 HXS (n-C3H7)2CHCOOCH2 X N N + R R1 4. 4a

-continued pR. pR. CH3CH-CH2 CH3CH2CH X=H, CONH2, CHNOR2, etc. 15 CH-COOR2; CH-COOR In another embodiment of like delivery system, appli- / s / cable for both the GABA and related compounds and CH3CH2CH2 CH3CH2CH2 for the carboxylic acids, or for any other drug species to 8 and 8a 9 and 9a be linked to such a carrier, either directly or indirectly, i.e. mediated by a carboxylic acid, e.g. succinic acido 20 Illustrative examples are the corresponding derivatives other linkage, provided is a mono- or poly-substituted of the 5-, 4-, and 3-hydroxy-2-n-propyl pentanoic acid nontoxic polyol (such as inositol or sugars) having the derivatives. Additional carrier systems, such as the trigonelline-dihydrotrigonelline system and the com- isoquinolinea-dihydroisoquinoline system, can also be pounds to be delivered linked to the same molecule as developed consistent herewith. exemplified by the GABA case (55a) and valproic 25 Moreover, based upon the observation that NADH acid (6-26a): content is significantly reduced in epileptic and like seizures, the use of the subject redox system (in reduced R4O OR4 form) will bias the NAD-2NADH balance towards NADH during the dihydro carrier->quaternary trans 30 formation. Also, the brain-specific delivery of small NH2CH2CH2CH2COO OR4; peptides consistent herewith, e.g., the enkephalins, which have been found to initiate epileptic seizures, has 5-S5a R4O OR4 led to the design of a variety of long lasting potent S antagonists. RaO OR 35 And the subject chemical delivery system is als 4. 4. useful for the delivery of other anticonvulsants in a sustained, brain-specific fashion, e.g., the benzodiaze (n-C3H7)2CH-COO OR4 pines and hydantoins, and those compounds, like apo morphine, which are useful in the treatment of photo 40 sensitive epilepsy. 6 S6a R4O OR4 It will of course be appreciated in the immediately above regard that the drug treatment of epilepsy has R4 = H, GABA or valproic acid, but at least one of R4. always posed formidable problems. There are many is: different anticonvulsants available, some more specific 45 for different types of seizures. Indeed, there exist a wide 2 variety of opinions as to which is the most suitable drug % for any particular type of seizure, and drug mixtures are CO CO typically employed. An inevitable result of the tradi O -N tional therapy is the development of chronic toxicity, 50 but such result is conspicuously avoided according to N. N the present invention. CH3 CH3 It too will be appreciated that the desired therapeutic (in 5a and 6a) (in 5 and 6) effects of all antiepileptic agents investigated, aS well as their undesired toxic effects, reflect a statistically signif R4 can be partially replaced by additional GABA or icant correlation with the drug levels in plasma. This valproic acid, changing the carrier/drug ratio as neces. Correlation is based upon a close relationship between sary. Some of the valproic acid metabolites can be cou- the drug concentrations in plasma and brain tissue. pled with carriers of the redox type, via the various Hence, a primary attribute of this invention is to enable hydroxy groups formed during the oxidative degrada- "" of high and sustained brain levels of the tion: 60 selected active agents, essentially against the plasma brain concentration gradient and independent of the drug concentration in the blood. R4-O-CH2CH2CH2 O GABA and related compounds are logical candi CH-C dates. It has been shown that GABA neuron function is CHCHCH / Yor 65 impaired in at least certain types of human epilepsy. 3-12-12 2 Animal studies also showed that seizures are induced by 7 and 7a reduction of GABA neuron function to a critical degree by (1) inhibition of GABA synthesis, (2) blockade of 4,540,564 41 42 GABA receptors or (3) inhibition of GABA-receptor tion (1970). Obviously, the choice of suitable carriers mediated ionic events. In addition, enhancement of will depend upon the exact nature of the particular GABA synaptic activity (by direct receptor stimulation dosage form selected, as well as upon the identity of the or by increasing GABA levels in the synapse) has a active drug species D. The therapeutic dosage ranges potent and wide spectrum anticonvulsant effect. These 5 for administration of the compounds according to this findings foreshadowed that an enhanced and sustained invention will generally be the same as, or less than, GABA brain delivery or a brain-specific delivery in a those characteristically used in this art for administra sustained manner of a good GABA-agonist would be tion of the known drug species D, per se. Naturally, efficacious in different forms of epilepsy. It is well such therapeutic dosage ranges will vary with the size known that GABA itself, when administered systemati O of the patient, the condition for which the D-DHC) cally, does not penetrate the normal blood-brain barrier compound is administered, the particular dosage form to any significant extent. Among the potential sites at employed, and the like. The quantity of given dosage which drugs may act to influence GABA-mediated form needed to deliver the desired dose of D will of synaptic function, the first target is to effect the BBB course depend upon the concentration of D-DHC) in transfer of GABA via a redox delivery system. The any given pharmaceutical composition/dosage form second main target is to effect the catabolism of GABA. 15 thereof. This invention, accordingly, specifically provides for The ability of the topic compounds to cross the BBB the efficacious delivery of the GABA-T inhibitors, and to be "locked into' the brain allows administration y-vinyl and y-acetylene-GABA, but the delivery of of the drug in a site-specific manner. A combination of valproic acid, specifically to the brain and without re the present dihydropyridine-pyridinium salt redox quiring high circulating blood levels, is also envisaged. 20 system with a sustained release system will further en In order to achieve the required activity, sodium val hance this site-specificity. Thus, a preferred embodi proate must have a relatively high, 50-100 ug/ml, level ment of the invention comprises formulating the D in the blood. The value of valproic acid is well estab DHC) compound or the salt of a D-DHC) compound lished in most types of epilepsy. It is evident that val utilizing a sustained release carrier system and/or route proic acid produces significant increases in both brain 25 of administration capable of slowly releasing the chemi and synaptosomal GABA concentrations Valproic acid cal, e.g., sustained release tablets and capsules for oral itself undergoes extensive metabolism. administration; subcutaneous injection, or implantation In capsule summary, the present invention provides of drugs in solid pellet form (for example, distributed in for the significantly improved treatment of epilepsy, a biodegradable polymer); intramuscular injection of and concomitant reduction in toxicity of a number of 30 the compound in solution in oil or suspended in a reposi antiepileptic drug species currently in use. And made tory vehicle; a transdermal delivery device or form available to the brain is a variety of important com such as an ointment to be applied locally to the desired pounds, such as GABA and a wealth of GABA-ergic site (when the drug is susceptible of delivery through agents. the skin), slow intravenous infusion and the like. The It will be apparent from the foregoing discussion of 35 rate of release of compound from the sustained release specific drug-carrier combinations that a wide variety system should be comparable to the rate of in vivo of synthetic approaches can be utilized, depending on oxidation of the dihydro form of the redox system in the chemical nature of the selected drug. Various illus order to achieve the greatest degree of enhancement of trative synthetic schemes as applied to specific centrally specificity. acting drugs in accord with this invention are set forth 40 below in the section entitled "Illustrative Synthetic Illustrative Synthetic Methods Methods'. While the sequence of reaction steps can be I. Methods for Derivatizing -NH2 or -NH varied in many cases, in general, the final step (except in Functions in Drugs the case of optional salt formation) will be reduction of a pyridinium compound of formula (II) to the corre Method A sponding dihydropyridine compound of formula (I). 45 The drug is reacted with nicotinoyl chloride, with The reduction is usually conducted at a temperature nicotinic anhydride, or with nicotinic acid in the pres from about -10° C. to room temperature, for a period ence of a suitable dehydrating agent such as dicyclohex of time from about 10 mins to 2 hrs, conveniently at ylcarbodiimide, in an appropriate organic solvent, to atmospheric pressure. Typically, a large excess of re afford the corresponding nicotinamide. The nicotina ducing agent is employed, e.g., a 1:5 molar ratio of 50 mide is then quaternized, typically by treatment with reducing agent to starting D-QC) compound. The methyl iodide in a suitable organic solvent, to afford the process is conducted in the presence of a suitable reduc quaternary derivative D-QC, which is then reduced ing agent, preferably an alkali metal dithionite such as by treatment with sodium dithionite or sodium borohy sodium dithionite or an alkali metal borohydride such as dride as generally described hereinabove to afford the sodium borohydride or lithium aluminum borohydride, 55 desired compound D-DHC). in a suitable solvent. Sodium dithionite reduction is The representative drugs listed below may be deriva conveniently carried out in an aqueous solution; the tized in this manner to the corresponding (D-QC and dihydro product D-DHC is usually insoluble in water D-DHC compounds. Tryptamine, desipramine and and thus can be readily separated from the reaction nortriptyline may be similarly derivatized. medium. In the case of sodium borohydride reduction, The foregoing procedure may be repeated using pico an organic reaction medium is employed, e.g., a lower linic acid or its acid chloride or anhydride, or isonico alkanol such as methanol, an aqueous alkanol or other tinic acid or its acid chloride or anhydride, in place of protic solvent. nicotinic acid or its acid chloride or anhydride, respec Suitable nontoxic pharmaceutically acceptable carri tively, to convert drugs such as those specifically men ers for use with the topic compounds D-DHC), e.g., 65 tioned for derivatizing by this Method to the corre those less toxic than the target drug species themselves, sponding picolinamides and isonicotinamides and then will be apparent to those skilled in this art. Compare, for to the corresponding (D-QC+ and D-DHC com example, Remington's Pharmaceutical Sciences, 4th Edi pounds.

4,540,564 55 56 The representative drugs listed below may be deriva Method B tized in this manner to the corresponding D-QC+ and This is a variation of Method A used when the drug D-DHC) compounds. Omega amino acids other than contains a -COOH function which is to be protected. GABA, other natural amino acids such as glycine, as The drug is first converted to the corresponding 5 partic acid and glutamic acid, and small peptides (2-20 ethyl ester by conventional esterification techniques. amino acids) may be similarly derivatized. That ester is then used as the starting material and The picolinamide and isonicotinamide quaternary Method A is repeated. and dihydro derivatives of the drugs specifically men Obviously, other esters may be similarly prepared in tioned for derivatizing according to this Method may be the first step by use of other esterifying agents. similarly prepared. See Method A.

15

25

30

35

45

50

55

60

65

4,540,564 63 64 Method C may be reversed, i.e. the drug may be first converted to the nicotinamide, which may then be reacted with This is a variation of Method A used when the drug trimethylacetylchloride to form the protected nicotina contains one or more OH functions which are to be mide. protected. 5 The drug is first reacted with excess trimethylacetyl Various other hydroxy protecting groups may be chloride to convert the hydroxy group(s) to pivalyloxy introduced in similar fashion. group(s). (This process is generally conducted in the The representative drugs listed below may be deriva presence of a base; however, strongly acid conditions tized in this manner to the corresponding D-QC+ and are used if an amine function is present.) That protected 10 D-DHC) compounds. The corresponding picolinamide derivative is then used as the starting material and sub and isonicotinamide quaternary and dihydro derivatives jected to Method A. Alternatively, the first two steps may be similarly prepared. See Method A.

15

20

25

35

45

50

55

60

65

4,540,564 69 70 in the presence of a suitable dehydrating agent, or with Method D nicotinoyl chloride or nicotinic anhydride, to form the This variation of Method A can be used when the corresponding nicotinic acid ester of the partial formula drug contains one or more OH and COOH functions which are to be protected. The protecting groups, typi- 5 cally the ethyl ester and pivalyloxy groups, are intro- N duced as described in Methods B and C, in the sequence considered most convenient. The amine function is Cl3C-CHOC O derivatized according to Method A. -- The representative drugs listed below may be deriva- 10 - -- tizedD-DHC) in this compounds. manner to Thethe corresponding corresponding (D picolinamide QC) and The resultant intermediate is then quaternized and re al disonicotiint id e quat ": N. d fdihydro ; o derivatiervatives ducedThe asrepresentative in Method A. starting drugs listed below may be may be similarly prepared. See Metnod A. derivatized in this manner to the corresponding

Starting Material D-QC)+ D-DHC) methyldopa NH2 + CH3 CH3 O N1 O N1 HO dCH-i-cooh CH3 NHC O NHC / / O O HO (CH3)3CCO CH-i-cooch, (CH3)3CCO CH-5-cooch, CH3 CH3 (CH).co (CH)ico O O levodopa HO CH2CHNH2 CH3 CH3 COOH O O N O O / N HO (CH3)3CCO Chhnic (CH3)3CCO CH-HNHC / COOC2H5 COOC2H5 (CHyacio (CH)cio O O

Method E D-QC+ and D-DHC compounds. Aminoglutethi This method is of particular use when the -NH mide, phenytoin, butalbital, methylphenidate, 3 function is a part of an amide or imide or a very low deazaguanine, PCNU, spiromustine, L-ICRF, demeclo pKa primary or secondary amine. 45 cycline, minocycline, doxycycline, oxytetracycline, The drug is first reacted with an aldehyde (e.g. form ethyl g-carboline 3-carboxylate and nifedipine may be aldehyde, benzaldehyde, acetaldehyde or chloral similarly derivatized. (Cl3CCHO)); for example, in the case of chloral, one The foregoing procedure may be repeated using pico converts the -NH-function to a linic acid or its acid chloride or anhydride, or isonico 50 tinic acid or its acid chloride or anhydride, in place of nicotinic acid or its acid chloride or anhydride, respec Cl3C-CHOH tively, to convert drugs such as those specifically men -N- tioned for derivatizing according to this Method to the corresponding picolinic acid esters and isonicotinic acid function and thus forms a suitable bridging group. The esters and then to the corresponding (D-QC+ and D resultant compound is then reacted with nicotinic acid 55 DHC compounds.

65

4,540,564 75 76 Similarly, Method F may be combined with Methods Method F B, C or D to afford the corresponding N-methyl-3- Method A is followed, except that in the first step, the quinolinecarboxamide derivatives, e.g. of the drugs listed with those methods. drug is reacted with 3-quinolinecarboxylic acid or its The foregoing procedure can be repeated using 4 acid chloride or anhydride instead of nicotinic acid or isoquinolinecarboxylic acid or its acid chloride or anhy its acid chloride. dride in place of 3-quinolinecarboxylic acid or its acid The representative drugs listed below may be deriva chloride or anhydride to convert drugs such as those tized in this manner to the corresponding D-QC and mentioned with Methods A, B, C or D to the corre D-DHC) compounds, as may the remaining drugs 10 sponding N-methyl-4-isoquinolinecarboxamide deriva listed with Method A. tives.

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4,540,564 83 84 Similarly, Method G may be combined with Methods Method G B, C or D to afford the corresponding derivatives, e.g. of the drugs listed with those methods. Method A is followed, except that in the first step, a The foregoing procedure can be repeated using pico starting material of the formula linic acid or its acid chloride or anhydride, or isonico tinic acid or its acid chloride or anhydride, in place of nicotinic acid or its acid chloride or anhydride, respec tively, in the preparation of the starting material. This O COOCH2COOH variation affords a starting material of the formula O N is used in place of nicotinic acid. (That starting material N COOCHCOOH or N O COOCH2COOH may be prepared by reacting nicotinic anhydride, nico tinoyl chloride or nicotinic acid with glycolic acid.) 15 The representative drugs listed below may be deriva O tized in this manner to the corresponding D-QC and which can then be used in place of nicotinic acid to D-DHC) compounds, as may the remaining drugs prepare derivatives of drugs such as those listed with listed with Method A. 20 Methods A, B, C or D.

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4,540,564 89 90 Similarly, Method H may be combined with Methods Method H B, C or D to afford the corresponding derivatives, e.g. Method A is followed, except that in the first step, a of the drugs listed with those methods. starting material of the formula The foregoing procedure can be repeated using 5 picolinamide or isonicotinamide in place of nicotina mide in the preparation of the starting material. This variation affords a starting material of the formula

N CONH (CH2)COOH wherein n = 1-3, preferably 2, is used in place of nico 10 (O) tinic acid. (That starting material may be prepared from N CONH2 or N nicotinamide, e.g. when n=2, by reacting 3-iodopro 15 (CH2)COOH (CH2)COOH pionic acid with nicotinamide.) The drugs listed below may be derivatized in this which can then be used in place of nicotinic acid in manner to the corresponding D-QC and D-DHC Methods A, B, C or D to form the corresponding deriv compounds, as may the remaining drugs listed with atives of drugs such as those listed with those methods. Method A. 20

Starting Material D-DHC) amphetamine CONH2 CH2CHCHNH, CH2CHCH3NHC-CHCH- O

CONH2 ()-airNHC-CHCH-N

-ur phentermine CH3 CONH2 ch,--NH. CH3 th CH-i-NHC-CHCH-N O th 9.

CONH2 ch,--NHC-CHCH-NCH3 --- O th I --

hydralazine SN S N CONH2 a N 1. N NH-NH2 NH-NH-CHCH-N-H O O 4,540,564 91 92 -continued Starting Material (D-Qc]+ (D-DHC) S N CONH Y N --- NH-NH-CHCH-N O -

II. Methods for Derivatizing -OH and -SH ribofuranosyl benzinidizole, 5,7-dimethyl-2-9-D- Functions in Drugs ribofuranosyl-s-triazole(1,5-a)pyrimidine, bisdihydrox yvinyluridine (BDVU), pholcodeine, meptazinol, cy Method I 15 clazocine, phenazocine, profadol, metopon, drocode, The drug is reacted with nicotinoyl chloride, with myfadol, buprenorphine, nalbuphine, butorphanol, lev nicotinic anhydride, or with nicotinic acid in the pres allorphan, naltrexone, alazocine, oxilorphan, nalmex ence of a suitable dehydrating agent such as dicyclohex one, idoxuridine, dipyridamole, estriol, cortoxdoxone, ylcarbodiimide, in an appropriate organic solvent, to fludrocortisone, paramethasone, oxogestone and tiges afford the corresponding nicotinate. The nicotinate is 20 tol may be similarly derivatized. then quaternized and subsequently reduced as described The foregoing procedure may be repeated using pico above in Method A. When the drug contains more than linic acid or its acid chloride or anhydride, or isonico one reactive hydroxyl or thiol function, reaction condi tinic acid or its acid chloride or anhydride, in place of tions may be varied so that more than one hydroxyl or nicotinic acid or its acid chloride or anhydride, respec thiol function will be converted to nicotinate groupings. 25 tively, to convert drugs such as those specifically men The representative drugs listed below may be deriva tioned for derivatizing by this Method to the corre tized in this manner to the corresponding D-QC) and sponding picolinic acid esters or isonicotinic acid esters D-DHC compounds. Ara-C, 2-deoxy-D-glucose, 2 and then to the corresponding (D-QC+ and (D-DHC) deoxy-2-fluoro-D-mannose, 5,6-dichloro-1-(3-D- 30 compounds.

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4,540,564 95 96

ZHO=Hotho, N

21 OORH

HOEO

HOEQ HO

Ionsabaou Iouensatu

4,540,564 101. 102 4,540,564 103 104

O

O || penu?uoo

4,540,564 105 106

ponu?uoo 4,540,564 107 108

panu?uoo 4,540,564 109 110

iC)

N

O O

&HOOO

N

HOOD

S N

4,540,564 117 18

tHO / NO

CHO=HOZHO

OCH

4,540,564 119 120

panu?uoo

IouousouAI 4,540,564 121 122

panu?uoo

4,540,564 125 126

4,540,564 129 130

panu?uoo

4,540,564 131 132

4,540,564 137 138

penu?uoo

4,540,564 143 144

ponu?uoo

4,540,564 145 146 4,540,564 147 148

ponu?uoo

4,540,564 149 150 4,540,564 151 152

4,540,564 153 154

4,540,564 163 164

4,540,564 167 168 Method J D-DHC compounds, as may the remaining drugs listed with Method I. This is a variation of Method I used when the drug Similarly, Method K may be combined with Method contains a -COOH function which is to be protected. J to afford the corresponding derivatives, e.g. of the The drug is first converted to the corresponding 5 drugs listed with that method. ethyl ester by conventional esterification techniques. A starting material of the formula set forth immedi That ester is then used as the starting material and ately above can also be substituted for nicotinic acid in Method I is repeated. The -COOH group may be Method E to afford the corresponding derivatives, e.g. similarly converted to other ester groups. of the drugs listed with that method. The representative drugs listed below may be deriva- 10 Method K may also be useful in preparing derivatives tized in this manner to the corresponding D-QC and of drugs in which the hydroxy function is hindered, e.g., D-DHC compounds. Diflunisal and clorazepate may biperiden, cycrimine, procyclidine and trihexyphenidyl. be similarly derivatized. Alternatively, Method K may follow Method I except The picolinic acid ester and isonicotinic acid ester that, in the first step, it employs a starting material of the quaternary and dihydro derivatives of the drugs specifi- 15 formula cally mentioned for derivatizing according to this method may be similarly prepared. See Method I. Starting Material (D-QC)+ D-DHC 5-hydroxy-2-n-propylpentanoic acid HO-CH2CH2CH2 O H3CNF a N O CH-C / N CO-CH2CH2CH2 O CH3CH2CH2 OH N Z CH-C / N CH3CH2CH2 OC2H5

H3C s N \ CO-CH2CH2CH2. O \ N 2 CH-e C / N CH3CH2CH2 OC2H5 4-hydroxy-2-n-propylpentanoic acid OH + CH3 CH3 CH3CHCH2 O N1 O / N1 CHCOOH OC O OC / / CH3CH2CH2 CHCHCH- CH3CHCH2 CH-Cooch, CH-cooch, CH3CH2CH2 CH3CH2CH2 3-hydroxy-2-n-propylpentanoic acid OH + CH3 CH3 CH3CH2CH O N1 O / N1 CH-COOH OC O OC / / CH3CH2CH2 CH3CH2CH CH3CH2CH CH-cooch, CH-cooch, CH3CH2CH2 CH3CH2CH2 Method K CONH2 Method I is followed, except that in the first step, a starting material of the formula (Ol CONH2 or (CH2)COOH O(CH2)COOH ar" 60 (prepared as described in Method H), to afford deriva tives of the drugs indicated with Method I. This alterna (CH2)COOH tive form of Method K may also be combined with 65 Method J, to afford the corresponding derivatives of wherein n = 1-3, preferably 2, is used in place of nico the drugs listed with Method J. Also, these alternative tinic acid. Method K starting materials may be substituted for The representative drugs listed below may be deriva nicotinic acid in Method E to give the corresponding tized in this manner to the corresponding (D-QC+ and derivatives of the drugs listed with that method.

4,540,564 171 172

penu?uoo

CHNOON ----OOHOO€H 4,540,564 173 174 Similarly, Method L may be combined with. Method Method L J to afford the corresponding derivatives, e.g. of the drugs listed with that method. Method I is followed, except that in the first step, the The procedure of Method L may be repeated using 4-isoquinolinecarboxylic acid or its acid chloride or drug is reacted with 3-quinolinecarboxylic acid or its anhydride in place of 3-quinolinecarboxylic acid or its acid chloride or anhydride instead of nicotinic acid or acid chloride or anhydride, to afford the corresponding derivatives of drugs such as those indicated with Meth its acid chloride. ods I and J. The representative drugs listed below may be deriva 10 3-Quinolinecarboxylic acid or its acid chloride or anhydride or 4-isoquinolinecarboxylic acid or its acid tized in this manner to the corresponding D-QCt and chloride or anhydride can also be substituted for nico D-DHC compounds, as may the remaining drugs tinic acid or its acid chloride in Method E to afford the corresponding derivatives, e.g., of the drugs listed with listed with Method I. 5 that method.

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4,540,564 179 180

+ N

4,540,564 181 182