Biochemically Directed Therapy of Leukemia with Tiazofurin, a Selective Blocker of Inosine 5'-Phosphate Dehydrogenase Activity1

(CANCER RESEARCH 49. 3696-3701. July I. 1989] Biochemically Directed Therapy of Leukemia with Tiazofurin, a Selective Blocker of Inosine 5'-Phosphate Dehydrogenase Activity1

Guido J. Tricot,2 Hiremagalur N. Jayaram, Elizabeth Lapis, Yutaka Natsumeda, Craig R. Nichols, Pat Kneebone, Nyla Heerema, George Weber, and Ronald Hoffman Division of Hematology/Oncology, Department of Medicine [G. J. T., C. R. N., P. K., R. H.]; Laboratory for Experimental Oncology [H. N. J., E. L., Y. N., G. W.]: and Department of Medical Genetics /A". //./ and the Indiana Elks Cancer Research Center f(i. J. T., R. H.Â¡,Indiana University School of Medicine, Indianapolis, Indiana 46223

ABSTRACT mology, and biochemistry of cancer cells (5, 6). In various cancer cells there is a marked enzymic imbalance Tiazofurin (2-/3-i>-ribofuranosylthiazole-4-carboxamide, NSC 286193), in purine metabolism, with strong evidence indicating up-reg- a selective inhibitor of the activity of IMP dehydrogenase (EC 1.1.1.205), ulation of the capacity for guanylate biosynthesis (5,6). Because the rate-limiting enzyme of de novo GTP biosynthesis, provided in end the activity of IMPDH, the rate-limiting enzyme of GTP bio stage leukemic patients a rapid decrease of IMP dehydrogenase activity synthesis, was increased in all examined cancer cells, it was and GTP concentration in the blast cells and a subsequent decline in blast cell count. Sixteen consecutive patients with end stage acute non- suggested that IMPDH should be a sensitive target of chemo lymphocytic leukemia or myeloid blast crisis of chronic granulocytic therapy (5-7). On the basis of this argument, a number of leukemia were treated with tiazofurin. Allopurinol was also given to compounds were prepared to block IMPDH activity, among inhibit xanthine oxidase activity to decrease uric acid excretion and to them tiazofurin (8), a C-nucleoside that is metabolized in two elevate the serum concentration of hypoxanthine, which should compet enzymic steps to thiazole-4-carboxamide adenine dinucleotide, itively inhibit the activity of hypoxanthine-guanine phosphoribosyltrans- an NAD analogue that selectively blocks IMPDH activity (9, ferase (EC 2.4.2.8), the salvage enzyme of guanylate synthesis. Assays 10). Tiazofurin in tissue culture and in the murine system of IMP dehydrogenase activity and GTP concentration in leukemic cells potently inhibited IMPDH activity, depressed GTP and dGTP provided a method to monitor the impact of tiazofurin and allopurinol concentrations, and yielded cytotoxicity and inhibition of tumor and to adjust the drug doses. In this group of patients with poor prognosis, cell proliferation (10, 11). Recent evidence indicated that, in five attained a complete hematological remission and one showed a hematological improvement. A marked antileukemic effect was seen in addition to an increase in IMPDH activity, the activity of the two other patients. All five Ã©valuablepatients with myeloid blast crisis guanine salvage enzyme HGPRT was also elevated in human of chronic granulocytic leukemia reentered the chronic phase of their leukemic cells (12-14). When human myeloid leukemic cells disease. Five patients with acute nonlymphocytic leukemia were refrac were incubated with radiolabeled tiazofurin, over 20-fold higher tory to tiazofurin and three were unevaluable for hematological effect concentrations of thiazole-4-carboxamide adenine dinucleotide because of early severe complications. Responses with intermittent 5- to were produced than in bone marrow cells from healthy volun 15-day courses of tiazofurin lasted 3-10 months. Tiazofurin had a clear teers (15, 16). These results provided support for the consider antiproliferative effect, but the pattern of hematological response indi ation of tiazofurin in the treatment of myelocytic leukemia. cated that it appeared to induce differentiation of leukemic cells. In spite of tnvidt) with severe or life-threatening complications in 11 of 16 Inhibition of IMPDH activity by tiazofurin in blast cells should decrease GTP and dGTP concentrations, which should restrain patients, tiazofurin was better tolerated in most patients than other antileukemic treatment modalities and provided a rational, biochemically the biosynthesis of DNA. Moreover, the blocking of guanylate targeted, and biochemically monitored chemotherapy which should be of biosynthesis might critically limit the availability of GTP for interest in the treatment of leukemias and as a paradigm in enzyme expression of the ras oncogene, G protein function, and the pattern-targeted chemotherapy. biosynthesis of specific proteins (Fig. 1). This approach was strengthened by the observation that the guanine-salvaging activity of HGPRT can be competitively inhibited by hypoxan INTRODUCTION thine and that the concentration of hypoxanthine can be mark edly increased in the plasma by allopurinol, originally given to Conventional antileukemic chemotherapy in relapsed or re fractory ANLL' patients is seldom curative and remissions, if block xanthine oxidase activity to decrease uric acid excretion (14). Therefore, to attain an optimal impact leading to depletion attained, are almost always of short duration. Myeloid blast of GTP in the blast cells, simultaneous administration of tia crisis of CGL is even more resistant to chemotherapy, with zofurin and allopurinol is essential. Since the action of tiazo complete hematological remission rates varying from 4 to 30% and median survivals being 6-29 weeks (1-4). A primary goal furin and allopurinol is well characterized, the biochemical impact of these drugs can be monitored during treatment by of antileukemic therapy in these patients with poor prognosis frequently sampling leukemic cells for measurement of IMPDH should be the identification of agents that are more selective activity and GTP concentrations. and better targeted in their actions. Such therapy should be based upon our increasing understanding of the biology, enzy- This paper reports our biochemically directed trial in patients with ANLL and myeloid CGL-BC, where tiazofurin rapidly Received 10/17/88: revised 3/30/89; accepted 4/6/89. brought down IMPDH activity and then GTP concentrations, The costs of publication of this article were defrayed in part by the payment followed by a decline in the blast cell count. of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. 1Supported by USPHS, National Cancer Institute. Outstanding Investigator Grant CA-42510 and Grant SO7 RR-5371 to G.W. MATERIALS AND METHODS 1To whom requests for reprints should be addressed, at the Division of Hemalology/Oncology, 541 Clinical Drive. Room 379, Indiana University School Patients. Sixteen consecutive patients were treated with tiazofurin at of Medicine. Indianapolis. IN 46223. 'The abbreviations used are: ANLL, acute nonlymphocytic leukemia; Indiana University Medical Center from March 1987 to April 1988. IMPDH, inosine 5'-phosphate dehydrogenase; CGL, chronic granulocytic leu The characteristics of the patients are listed in Table 1. This Phase I/ kemia: CGL-BC, blast crisis of chronic granulocytic leukemia; HGPRT, hypo II trial was monitored by the Cancer Therapy Evaluation Program, xanthine-guanine phosphoribosyltransferase: MDS, myelodysplastic syndrome. Division of Cancer Treatment, National Cancer Institute (Bethesda, 3696

according to the principles of the Declaration of Helsinki. The protocol had been reviewed and approved by the Investigational Review Board of the Indiana University School of Medicine. Biochemical Assays. Preparation of bone marrow and peripheral blood mononuclear cells and determination of the concentration of GTP were carried out as reported (15). Briefly, mononuclear cells were separated by a Ficoll-Paque density gradient. An aliquot of cells was then extracted with 10% trichloracetic acid, neutralized immediately with tri-n-octylamine in Freon, and analyzed by high pressure liquid chromatography for GTP concentrations, using a buffer system of ammonium phosphate. Another aliquot of cells was assayed directly for IMPDH activity as described (20). During treatment with tiazofurin, IMPDH activity and GTP pools in leukemic cells were measured at least 3 times/day in peripheral blood samples. Chromosome Preparation and Analysis. Cytogenetic investigations were performed on bone marrow or peripheral blood using direct analysis, short term incubation for 24 li. or culturing without phyto- hemagglutinin for 48 h. Chromosome preparations were studied at >400-band level (21). Drug and Administration. Tiazofurin in sterile injectable form was obtained from the National Cancer Institute (Bethesda, MD). The drug was administered daily, over a period of 1 h, by an infusion pump (Imed Fig. I. Pathways of IMP and GTP metabolism and the biochemical basis for the chemotherapeutic impact of tiazofurin and allopurinol. Gua, guanine; GPRT, Co., San Diego, CA) under sterile conditions. Uniformity in treatment guanine phosphoribosyltransferase. protocol was provided by biochemical targeting to decrease GTP con centrations to <20% of control; therefore, individual schedules were MD). Patients reported on here suffered from refractory or relapsed required, involving variations in tiazofurin dose. In the first patient in ANLL, treatment-related ANLL, ANLL after a myelodysplastic syn the study (patient 9), the initial dose was 1100 mg/nr, based on data drome, or nonlymphoid blast crisis of CGL, based on morphology and from previous Phase I trials. This dose was too low to decrease GTP immunological markers (negative for Tdt and the common acute Km levels. Therefore, all subsequent patients were initially given 2200 mg/ m2 (an exception was patient 1, who received 5800 mg/nr the first day phocytic leukemia antigen and positive for at least one of the myeloid markers, VIM-2, My 9, and My 7). Eligibility criteria required a first because of a mistake made in the hospital pharmacy). The different remission duration of <12 months; however, the initial remission timings of dose escalations were based on the biochemical response; duration in patients I and 8 was 18 and 13 months, respectively. Patient the goal was to avoid unnecessary dose escalations. If an insufficient 11 on admission had serum bilirubin >1.S mg/dl. The initial clinical decline occurred in GTP levels, further dose escalations were initiated. course of the first patient studied (patient 9) was published (16). At the end of the study, we concluded that the best results are obtained Evaluation of Response. A complete remission was defined by stand by escalating uniformly after 3 days in the case of lack of decrease in ard criteria (17). Hematological improvement was defined as a bone GTP concentration to <20% and that each treatment course should be marrow blast count of <5% within the peripheral blood, absolute no longer than 15 days. granulocyte count of > 1.0 x 10'/liter, and a platelet count of >50 x Tiazofurin at the effective dose was then administered until the lO'/Hter (18). Antileukemic effect was defined as a complete disap peripheral blood was cleared of blast cells. This pattern of administra pearance of all blasts from the peripheral blood with a bone marrow tion was followed in all the patients except for the first one (patient 9) blast count of <5%. Patients who did not meet these criteria were who was treated with tiazofurin for only 5 days at the effective dose. considered nonresponders. Patients who attained a complete remission or hematological improve Evaluation of Toxicity. Toxicity was evaluated according to the ment received further courses of tiazofurin as consolidation treatment criteria of the Eastern Cooperative Oncology Group (19). (patient 1) or whenever an increase in absolute numbers of blast cells Informed Consent. Informed consent was obtained from all patients (> 5 x lO'/Hter) was noted in the peripheral blood (patients 2-6 and

Table 1 Patients' characteristics, total dose and number of days of initial tiazofurin treatment, outcome, and duration of response

dose of tiazofurin of du- sur PatientSex/AgeDiseaseStatusTotal(mo)Responders12345678F/53M/21F/20M/44M/56F/58M/70M/55ANLLCGLCGLCGLCGLCGLANLLANLLFirst(mg/m2)No. daysResponse Outcome ration (mo)Total vival

relapseMyeloid 10Completeremission crisisMyeloidblast 3Complete response crisisMyeloidblast 6Complete response crisisMyeloidblast 7Complete response crisisMyeloidblast 6Hematologicalresponse crisisSecondaryblast 10Antileukemic improvement leukemiaFirst <1Antileukemiceffect <11546'131316<1

relapseSecond responseNo relapseRefractory responseNo relapseFirst first responseNo relapseFirst responseNo response42<126Unevaluable relapse23,65049.50052,50027,50020.9001118201010No effect141516M/83F/50M/27ANLLANLLCGLPostfor hematological MDSPost MDSMyeloid blast crisis14,3005,5002.200531UnevaluableUnevaluableUnevaluable<18<1 " Patient returned to primary1 physician, in California, who treated her there with mitoxanthrone to prepare her for bone marrow transplantation, but patient died during mitoxanthrone chemotherapy. 3697

9). During these intermittent courses, the dose of tiazofurin was esca and blast cells. In patients 11 and 12, who were refractory to lated in some patients to 6600 mg/nr, if an inadequate decline in GTP tiazofurin treatment, IMPDH activity remained elevated and levels was seen. GTP pools were never depressed to <20% of pretreatment On admission, a permanent central line was placed in all patients. values. Patients 1-6 and 9 received multiple courses of tiazo When neutropenic, patients received antimicrobial prophylaxis with furin treatment. Clinical relapse of the disease in patients 2-6 norfloxacin and ketoconazole. While receiving tiazofurin, all patients were placed on allopurinol, 300 mg/day or 100 mg every 4-6 h. and 9 was always associated with marked increases in IMPDH Allopurinol was given initially to prevent hyperuricemia (300 mg/day). activity and GTP pools in the leukemic cells. Reinstitution of Subsequently, divided doses of allopurinol (100 mg, 4 to 8 times/day) tiazofurin (Fig. 3) was accompanied by a biochemical and were given in an attempt to maintain high and more constant hypoxan- hematological response similar to that observed during the thine levels in the serum. Depletion of GTP in blast cells depended on initial treatment. This pattern was seen with all retreatment both tiazofurin and allopurinol, to block the de novo and salvage courses except during the fifth course of treatment in patient 9; pathways, respectively. he became refractory to tiazofurin by both biochemical and hematological parameters. RESULTS Clinical Response to Tiazofurin. Outcome of treatment and duration of response are provided in Table 1. Peripheral blood Biochemical Parameters during Tiazofurin Treatment. A cor cell counts obtained from responders prior to, at the end of, relation between biochemical and hematological responses was and 7-10 days after treatment are given in Table 2. Bone seen in all patients. Figs. 2 and 3 are typical of positive re marrow cellularity, bone marrow cell differential counts, and sponses; they were absent when clinical treatment failed. Insti cytogenetic analyses of these responders are shown in Table 3. tution of tiazofurin therapy resulted in a rapid decrease in Five patients, one with ANLL and four with CGL-BC, at IMPDH activity. The decline in GTP pools occurred more tained a complete hematological remission. The patient with slowly, and dose escalations were necessary in most patients to ANLL also entered a cytogenetic remission, while chromosome reach a >80% decline. The decline in GTP pools was followed abnormalities persisted in the patients with CGL-BC. One by a rapid decrease in the absolute numbers of peripheral WBC patient with CGL-BC showed a hematological improvement. In two patients with ANLL a marked antileukemic effect was seen; both patients died, however, from invasive fungal infec TIAZOFURIN (mg/m ) tions. Five patients were classified as therapy failures, although some antileukemic effect was seen in three of these (patients 9- 2200 3300 n rrr~n 11), with a >75% decrease in the absolute number of peripheral blasts in all three and a >75% decrease in bone marrow blasts in patient 9 (16). 120-1 The hematological effect of tiazofurin was not Ã©valuablein three patients because of early severe or life-threatening toxicity, consisting of seizures (patient 14), pleuropericarditis (pa â€¢WBC tient IS), and sudden coma (patient 16). Most of the responders maintained a granulocyte count of 100- O BLAST >0.5 x 109/liter during and after treatment. Patients 1, 3, and A CTP 4 showed an increase in platelet counts after tiazofurin treat UJ IMP DH ment. 80- Bone marrow specimens obtained during and shortly after treatment remained normo- or hypercellular in all responders Z except patients 4 and 8 (Table 3). Posttreatment bone marrow 01 S aspirates in responders showed a shift from blast cells to more H 60- mature cells, except in patient 8, who received 25 days of UJ tiazofurin and became severely hypoplastic after treatment. The complete remission in patient 1 lasted for 10 months. UJ U. The duration of response in the CGL-BC patients was 3, 6, 6, 0. 10- LL 7, and 10 months. Patient 2 became clinically refractory to O treatment after 3 months; at that time, he had developed an af> additional chromosome abnormality. After four cycles of good response, patient 3 discontinued treatment to undergo an allo- 20- geneic bone marrow transplantation with an unrelated donor. Patients 4-6 remained clinically and biochemically sensitive to tiazofurin but preferred to be switched to oral antileukemic therapy. Two of these patients were refractory to hydroxyurea

TIAZOFURIN (mg/mÂ¿ ) rm2200 rm3300 rm3300 rm3300 250-, 200- Fig. 3. Changes in hematological and bio 150- chemical parameters during two consecutive 120- courses of tiazofurin treatment in patient 4. The values of WBC, blast cells, GTP pools, and IMPDH activity are expressed as a per centage of pretreatment values. The pretreat ment value of WBC was 6.6 x lO'/Hter; blast cells, 4.0 x lO'/liter; GTP pools, 344.3 nmol/ 10' leukemic cells; and IMPDH activity, 12.2 nmol/h/mg protein.

i 5 ; 9 24 26 28 30

TREATMENT (days)

Table 2 Effect of tiazofurin therapy on peripheral blood counts of patients who responded to tiazofurin therapy Values represent absolute numbers of specific cellular elements. WBC(xlO'/liter) Blasts (x lO'/Hter) Granulocytes (x lO'/liter) Platelets (x lO'/liter) PreÂ° End* Post' Patient Pre End Post Pre End Post Pre End Post 11.32 148.03 6.64 12.65 94.06 19.07 111.38 17.41.522.12.41.59.85.47.50.44.04.06.03.21.64.12.60.70.440.04.01.019.77.446.512.70.00.00.10.00.00.30.00.010.00.00.00.20.30.10.00.00.422.20.24.833.06.530.63.80.315.00.61.08.93.86.00.03.12.41.61.00.83.22.10.039.0124.019.0''524.0203.065.041.0''94.062.0136.046.0134.038.050.034.0"9.0a143.0149.0125.0210.0194.050.023.0''IS.O* Â°Prior to the institution of therapy. * On the day therapy was discontinued. '7-10 days after discontinuation of therapy. '' Patient receiving platelet transfusions.

Table 3 Bone marrow findings before and after tiazofurin treatment in the eight responders

Cellularity"Patient1 (%)Before36C (%)Before22028+ Gran {*Before029)After1515

2 Hyper Hyper NE t(9;22) t(9;22) 3 Hyper Hyper 55 t(9;22),+21 t(9;22),+21 4 Hyper Hypo 33 2 28 20 54 t(8;22),+8,+ 12,der(22) t(8;22),+8,+ 12,+d S Hyper Normal 48 2 8 14 41 72 t(9;22) t(9;22) 6 Hyper Hyper 25 510Pro'-t- 14 0 45 74 t(9;22)i(17q),del(6q) t(9;22)i(l7q)del 7 Hyper Hyper 60 12 6 510After787593 -7,del(17q) ND 8BeforeHypoNormalAfterNormalHypoBlasts 82After04 1Myelo 0MM 0CytogeneticsBeforeInv(16),+22NormalAfterNormal No mitoses " Cellularity was estimated in bone marrow biopsies or aspirates. * Pro, promyelocytes; Myelo, myelocytes; MM, metamyelocytes; Gran, granulocytes; NE, not Ã©valuablebecauseof dry tap; ND, not done. ' Percentage of cells on a 200 cell marrow differential of a Wright-Giemsa-stained bone marrow aspirate specimen. derlying hematological disorder. Most of the toxic events (66%) apy could be resumed without reappearance of clinical symp were mild or moderate. The most common side effect was toms of pleuropericarditis in three patients. drowsiness. Patients with drowsiness were easily arousable and Patient 12 developed a pericardia! friction rub during his were fully awake by the time the next infusion was given. Other second course of tiazofurin; he quickly improved on cortico- mild and moderate toxicities noted were nausea, vomiting, steroids and tiazofurin therapy was restarted. However, 9 days headaches, myalgias, conjunctivitis, skin rash, and atrial fibril after the completion of treatment, he was readmitted to the lation. hospital with fever, skin lesions, swelling of both knees, severe Five patients developed clinical signs of pleuropericarditis. neutropenia, and progressive leukemia. A pericardia! friction In all five patients, pain due to the serositis improved within rub was noted. Echocardiogram performed 5 days later showed 48 h after discontinuation of tiazofurin and institution of cor- a large pericardia! effusion and the patient died from the ticosteroids. Chest X-rays and echocardiograms remained nor consequences of cardiac tamponade. Patient 15 developed acute mal. One patient had electrocardiogram changes suggestive of chest pain and shortness of breath after 3 days of tiazofurin. pericarditis; in another patient the pericarditis was associated She recovered completely but received no further treatment. with atrial fibrillation requiring digitalization. Tiazofurin ther Three patients developed life-threatening infections. Patients 7 3699

Table 4 Konhematological toxicily observed with tia:ofurin treatment Group A, 11 patients treated for less than 15 days and without major complicating medical problems at entrance in the protocol; group B. 5 patients treated for longer than 15 days or entering trial with major complicating medical problems.

MildModerateSevereLife-threaten-ingSymptoms

signsDrowsiness,and confusionInfectionNausea/vomitingPleuropcricarditisLiver

abnormalitiesHeadachesCardiacfunction

toxicitySkin rashMyalgiasHypertensionSeizuresC'omaA1030010(1(10(10B200010000000A622011111200B2i1001011000A100400000000B000020000000A010100000020B020000200002

and 8 developed invasive fungal infections and patient 14 an prolonged if an oral formulation of tiazofurin were available. aspiration pneumonia. Patients 6 and 14 developed seizures An alternative approach may be to maintain the initial response which were difficult to control and they needed multiple anti- with oral antileukemic agents such as hydroxyurea and 6- convulsant drugs. Patient 6 recovered completely and tiazofurin thioguanine. These agents appeared to be active in three of our therapy could be restarted; she experienced a second episode of patients after tiazofurin therapy. seizures at a higher dose of tiazofurin. Patient 14 remained The unique aspect of the tiazofurin-allopurinol therapy was somnolent and confused and subsequently died of an aspiration the manner in which the dose of therapy was guided by cellular pneumonia. biochemical parameters. Drug dosage was determined by sam Two patients showed a marked increase in liver function pling residual leukemic cells from either peripheral blood or abnormalities. Patient 8 was being given broad spectrum anti bone marrow and determining GTP pools and IMPDH activity. biotics, acyclovir, and amphotericin B for septicemia and esoph- A marked decline in IMPDH activity and GTP pools was agitis with Candida albicans and herpes simplex; patient 11 followed by a hematological response. The duration of treat already had impaired liver function before the start of tiazo ment was determined by biochemical and hematological (WBC furin. and blast cell count) parameters. Two patients developed sudden coma. Patient 11 had an It is yet unknown whether tiazofurin acts solely as an anti- infection, was on broad spectrum antibiotics, and was com proliferative agent or whether it may also induce maturation of pletely refractory to platelet transfusions. Patient 16 was ad leukemic cells. Observations from an ANLL patient who mitted with a WBC count of 282 x IfT/liter and 79% blasts. achieved complete remission with loss of her marker chromo He presented with clinical findings consistent with a hyperleu- somes and from one patient who developed severe marrow kocytic syndrome. He was subjected to leukapheresis twice and hypoplasia after prolonged tiazofurin therapy provide us with tiazofurin therapy was then started. He abruptly developed clinical evidence that this drug clearly has an antiproliferative coma with signs of decerebration, intractable hypotension, and effect. In contrast, the absence of bone marrow hypoplasia, the respiratory failure, 6 h after the completion of the first dose of marked shift from blast cells to mature granulocytes in the bone tiazofurin. He died the next day; autopsy was refused. Two marrow, the persistence after the cessation of tiazofurin admin patients experienced ventricular fibrillation and cardiac arrest istration of adequate numbers of granulocytes and platelets, (patients 8 and 11). and the persistence of chromosome abnormalities observed in the other responding patients provide evidence that this drug promoted leukemic cell differentiation in vivo (Table 3). This DISCUSSION suggestion is supported by in vitro studies with tiazofurin in The results of this Phase I/II trial with tiazofurin in leukemia human leukemic cell lines (23-25). However, the possibility are very encouraging because five patients (31%) attained a that tiazofurin induces maturation of leukemic cells /// vivo complete remission, one (6.5%) had a hematological improve must be substantiated by further clinical investigations. ment, and two showed a marked antileukemic effect (12.5%). Toxicity has been well described in Phase I trials with tiazo Objective responses (complete and partial) in Phase I trials furin (26-31). Toxicity was also substantial in this trial. The between 1974 and 1982 were reported in 5.8% of leukemic most severe complications, however, such as sudden coma, patients, while the best reported complete and partial response ventricular fibrillation, and cardiac tamponade, were seen in rates in Phase II trials with the four drugs considered to be patients with either complicating medical problems such as active in leukemia, aclarubicin, amsacrine, azacytidine, and hyperviscosity syndrome, abnormal liver function, and progres zorubicin, were 21, 20, 14, and 44%, respectively (22). Espe sive leukemia or prolonged treatment with tiazofurin (over 15 cially the results with tiazofurin in nonlymphoid blast crisis of days), resulting in bone marrow hypoplasia with infectious CGL appear very promising. All five hematologically Ã©valuable complications. The exact contribution of tiazofurin to these patients with CGL-BC returned to the chronic phase of their severe toxicities is therefore difficult to determine. As Table 4 disease. The duration of complete remission in one ANLL shows, toxicity was lower in patients who entered the study patient was 10 months. The response in CGL-BC was short with few complications and were treated for less than 15 days lived (2-6 weeks), but patients returned to the chronic phase in each cycle. More severe and life-threatening toxicity occurred with reinstitution of tiazofurin treatment. The total duration of in patients who entered in a severely compromised status and response in these patients was 3, 6, 6, 7, and 10 months. It is were treated longer than 15 days in the cycles. In future trials, likely that the initial response in CGL-BC could be considerably we would recommend the restriction of tiazofurin treatment to 3700

Downloaded from cancerres.aacrjournals.org on September 27, 2021. © 1989 American Association for Cancer Research. TIAZOFURIN TREATMENT OF LEUKEMIA thiazole-4-carboxamide to an analogue of NAD with potent IMP dehydrog- patients in stable clinical condition without complicating med enase inhibitory properties. Biochem. Pharmacol., 31: 2133-2136. 1982. ical problems; the total duration of treatment should not exceed 10. Jayaram. H. N., Dion, R. L.. Glazer. R. !.. Johns, D. G.. Robins, R. K., 10 to 15 days/course. Drowsiness was quickly reversible after Srivastava. P. C., and Cooney, D. A. Initial studies on the mechanism of action of a new oncolytic thiazole nucleoside, 2-tf-n-ribofuranosylthiazole-4- discontinuation of therapy and never resulted in medical prob carboxamide (NSC 286193). Biochem. Pharmacol.. 31: 2371-2380, 1982. lems. Myalgias and pleuropericarditis rapidly responded to 11. Lui, M. S., Faderan, M. A., Liepnieks, J. J.. Natsumeda, Y.. Olah, E.. temporary discontinuation of the tiazofurin and/or institution Jayaram, H. N.. and Weber. G. Modulation of IMP dehydrogenase activity and guanylalc metabolism by tiazofurin (2-^-D-ribofuranosylthiazole-4-car- of prednisone therapy; myalgias and pleuropericarditis did not boxamide). J. Biol. Chem., 259: 5078-5082, 1984. prevent further therapy with tiazofurin. Seizures were preceded 12. Becher, J. F., and Lohr, E. W. Inosine 5'-phosphate dchydrogcnase in normal by hypertension; since we promptly instituted antihypertensive and leukemic blood cells. Klin. Wochenschr.. 57: 1109-1115. 1974. 13. Price, G. M., Hoffbrand, V., Talleri, M. R., and Evans, J. P. M. Inosine therapy with calcium channel blockers in patients with hyper monophosphate dehydrogenase activity in acute leukemia. Leuk. Res.. Ã•I: tension, no new seizures have been observed. 525-530. 1987. 14. Weber. G., Jayaram. H. N., Lapis. E.. Natsumeda. V., Yamada, Y.. Yamaji. Novel aspects of this study include the following, (a) The Y'., Tricot. G. J.. and Hoffman. R. Enzyme-pattern-targeted chemotherapy clinical trial was rationally targeted against the enzyme pattern with tiazofurin and allopurinol in human leukemia. Adv. Enzyme Regul., 27: of elevated IMPDH and HGPRT activities in the leukemic 405-433. 1988. 15. Jayaram, H. N., Pillwein. K., Nichols, C. R., Hoffman, R., and Weber, G. blast cells, (b) Infusion of tiazofurin rapidly decreased IMPDH Selective sensitivity to tiazofurin of human leukemic cells. Biochem. Phar activity and curtailed GTP concentrations in the blast cells, macol., 35: 2029-2032, 1986. yielding a clearing of blast cells (c) Measurement of the behavior 16. Tricot. G. J.. Jayaram, H. N., Nichols, C. R., Pennington. K., Lapis, E., Weber, G., and Hoffman, R. 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Downloaded from cancerres.aacrjournals.org on September 27, 2021. © 1989 American Association for Cancer Research. Biochemically Directed Therapy of Leukemia with Tiazofurin, a Selective Blocker of Inosine 5 ′-Phosphate Dehydrogenase Activity

Guido J. Tricot, Hiremagalur N. Jayaram, Elizabeth Lapis, et al.

Cancer Res 1989;49:3696-3701.

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