pharmaceuticals Article Preclinical Pharmacokinetics and Biodistribution of Anticancer Dinuclear Palladium(II)-Spermine Complex (Pd2Spm) in Mice Martin Vojtek 1,* , Salomé Gonçalves-Monteiro 1, Edgar Pinto 2,3,Sára Kalivodová 1, Agostinho Almeida 4 , Maria P. M. Marques 5,6 , Ana L. M. Batista de Carvalho 5 , Clara B. Martins 5, Helder Mota-Filipe 7 , Isabel M. P. L. V. O. Ferreira 2 and Carmen Diniz 1,* 1 LAQV/REQUIMTE, Laboratory of Pharmacology, Department of Drug Sciences, Faculty of Pharmacy, University of Porto, 4050-313 Porto, Portugal; [email protected] (S.G.-M.); [email protected] (S.K.) 2 LAQV/REQUIMTE, Laboratory of Bromatology and Hydrology, Department of Chemical Sciences, Faculty of Pharmacy, University of Porto, 4050-313 Porto, Portugal; [email protected] (E.P.); [email protected] (I.M.P.L.V.O.F.) 3 Department of Environmental Health, School of Health, P.Porto, CISA/Research Center in Environment and Health, 4200-072 Porto, Portugal 4 LAQV/REQUIMTE, Laboratory of Applied Chemistry, Department of Chemical Sciences, Faculty of Pharmacy, University of Porto, 4050-313 Porto, Portugal; [email protected] 5 “Molecular Physical-Chemistry” R&D Unit, Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal; [email protected] (M.P.M.M.); [email protected] (A.L.M.B.d.C.); Citation: Vojtek, M.; [email protected] (C.B.M.) 6 Gonçalves-Monteiro, S.; Pinto, E.; Department of Life Sciences, University of Coimbra, 3000-456 Coimbra, Portugal 7 iMed.ULisboa, Faculty of Pharmacy, University of Lisbon, 1649-003 Lisbon, Portugal; hfi[email protected] Kalivodová, S.; Almeida, A.; Marques, * Correspondence: [email protected] (M.V.); [email protected] (C.D.) M.P.M.; Batista de Carvalho, A.L.M.; Martins, C.B.; Mota-Filipe, H.; Abstract: Palladium-based compounds are regarded as potential analogs to platinum anticancer Ferreira, I.M.P.L.V.O.; et al. Preclinical drugs with improved properties. The present study assessed the pharmacokinetics and biodistri- Pharmacokinetics and Biodistribution bution of a dinuclear palladium(II)-spermine chelate (Pd Spm), which has previously been shown of Anticancer Dinuclear 2 Palladium(II)-Spermine Complex to possess promising in vitro activity against several therapy-resistant cancers. Using inductively (Pd2Spm) in Mice. Pharmaceuticals coupled plasma-mass spectrometry, the kinetic profiles of palladium/platinum in serum, serum 2021, 14, 173. https://doi.org/ ultrafiltrate and tissues (kidney, liver, brain, heart, lungs, ovaries, adipose tissue and mammary 10.3390/ph14020173 glands) were studied in healthy female Balb/c mice after a single intraperitoneal bolus injection of Pd2Spm (3 mg/kg bw) or cisplatin (3.5 mg/kg bw) between 0.5 and 48 h post-injection. Palladium in Academic Editor: serum exhibited biphasic kinetics with a terminal half-life of 20.7 h, while the free palladium in serum Daniela Montesarchio ultrafiltrate showed a higher terminal half-life than platinum (35.5 versus 31.5 h). Palladium was distributed throughout most of the tissues except for the brain, with the highest values in the kidney, Received: 29 January 2021 followed by the liver, lungs, ovaries, adipose tissue and mammary glands. The in vitro cellular accu- Accepted: 17 February 2021 mulation was also evaluated in breast cancer cells, evidencing a passive diffusion as a mechanism Published: 23 February 2021 of Pd2Spm’s cellular entry. This study reports, for the first time, the favorable pharmacokinetics and biodistribution of Pd2Spm, which may become a promising pharmacological agent for cancer Publisher’s Note: MDPI stays neutral treatment. with regard to jurisdictional claims in published maps and institutional affil- iations. Keywords: Pd(II)-based drugs; cisplatin; ICP-MS; metal complexes; polyamines; cancer; tissue; in vivo Copyright: © 2021 by the authors. 1. Introduction Licensee MDPI, Basel, Switzerland. This article is an open access article The discovery of the anticancer properties of the platinum(II)-based drug cisplatin distributed under the terms and (cis-Pt(NH3)2Cl2) (Figure1a) has revolutionized the therapy of solid neoplasms, namely, conditions of the Creative Commons breast, testicular, ovarian, cervical, prostate, head, neck, bladder and lung cancers, as well Attribution (CC BY) license (https:// as refractory non-Hodgkin’s lymphoma [1]. However, its therapeutic use is limited by creativecommons.org/licenses/by/ inherent or acquired tumor cell resistance and dose-dependent toxicity (namely, nephrotox- 4.0/). icity, hepatotoxicity, neurotoxicity and myelosuppression). To overcome these limitations, Pharmaceuticals 2021, 14, 173. https://doi.org/10.3390/ph14020173 https://www.mdpi.com/journal/pharmaceuticals Pharmaceuticals 2021, 14, x FOR PEER REVIEW 2 of 16 Pharmaceuticals 2021, 14, 173 inherent or acquired tumor cell resistance and dose-dependent toxicity (namely,2 of 16ne- phrotoxicity, hepatotoxicity, neurotoxicity and myelosuppression). To overcome these limitations, several modifications of cisplatin’s structure have led to the development of carboplatin and oxaliplatin, which have also received worldwide approval for clinical use. several modifications of cisplatin’s structure have led to the development of carboplatin Carboplatin (Figure 1b) is a 2nd generation platinum drug with an improved pharmaco- and oxaliplatin, which have also received worldwide approval for clinical use. Carbo- kinetic profile and tolerability, owing to the substitution of the two chloride ligands by a platin (Figure1b) is a 2nd generation platinum drug with an improved pharmacokinetic cyclobutanedicarboxylate group that has a slower hydrolysis rate to yield reactive species profile and tolerability, owing to the substitution of the two chloride ligands by a cyclobu- prone to bind to DNA [2]. Carboplatin is indicated in a monotherapy regimen of ovarian tanedicarboxylate group that has a slower hydrolysis rate to yield reactive species prone toand bind small to DNA cell lung [2]. carcinomas, Carboplatin but is indicatedit shares a in cross-resistance a monotherapy with regimen cisplatin of ovarianin previously and smallcisplatin-treated cell lung carcinomas, patients, which but it limits shares its a clinical cross-resistance use [3]. Oxaliplatin with cisplatin (Figure in previously 1c) is a 3rd cisplatin-treatedgeneration platinum patients, analog which with limits a diaminocyclohexane its clinical use [3]. ligand Oxaliplatin that significantly (Figure1c) is reduces a 3rd generationits toxicity platinum and glutathione-mediated analog with a diaminocyclohexane acquired tumorligand cell resistance that significantly [4]. Although reduces oxali- its toxicityplatin is and less glutathione-mediated reactive towards DNA acquired than tumorcisplatin, cell it resistance was demonstrated [4]. Although in vitro oxaliplatin that its iscrosslinks less reactive appear towards to be DNA more than damaging cisplatin, [5]. it Currently, was demonstrated oxaliplatinin vitro in combinationthat its crosslinks with 5- appearfluorouracil to bemore is approved damaging for [the5]. Currently,treatment oxaliplatinof advanced in colorectal combination cancer. with 5-fluorouracil is approvedThe pharmacodynamic for the treatment ofeffects advanced of cisplatin colorectal and cancer. other platinum agents are generally acceptedThe pharmacodynamic to be mediated by effectsthe binding of cisplatin to DNA and in otherthe nucleus platinum and agents mitochondria, are generally while acceptedother non-DNA to be mediated targets, bysuch the as binding RNA, tubu to DNAlin, thioredoxin in the nucleus reductase, and mitochondria, membrane-bound while otherNa+/H non-DNA+ exchanger targets, protein such [6], as or RNA, even tubulin, intracellu thioredoxinlar water reductase,[7], have also membrane-bound been reported. NaUpon+/H +cellularexchanger entry, protein the drug’s [6], or hydrolyzab even intracellularle ligands water are [substituted7], have also with been water reported. mole- Uponcules, cellular yielding entry, highly the drug’sreactive hydrolyzable aqua specie ligandss that bind are substitutedto DNA (mainly with water through molecules, the pu- yieldingrine´s nitrogen highly atoms) reactive [8]. aqua The speciesformation that of bindthese todrug-DNA DNA (mainly adducts through prompts the DNA purine’s dam- nitrogenage, which atoms) interferes [8]. The with formation the replication of these and drug-DNA transcription adducts processes prompts and DNA leads damage, to cell whichgrowth interferes impairment with and the replicationcellular death and [2]. transcription processes and leads to cell growth impairment and cellular death [2]. (a) (b) (c) (d) FigureFigure 1. 1.Structure Structure of of Pt(II)- Pt(II)- andand Pd(II)-basedPd(II)-based agents: Worldwide approved approved Pt Pt drugs—( drugs—(aa)) cisplatin, cisplatin, (b (b) )carboplatin carboplatin and and (c) oxaliplatin. (d) Novel palladium(II)-based complex Pd2Spm. (c) oxaliplatin. (d) Novel palladium(II)-based complex Pd2Spm. DespiteDespite the the indisputable indisputable role role of of mononuclear mononuclear platinum platinum drugs drugs (compounds (compounds with with one one metalmetal center, center, such such as as cisplatin, cisplatin, carboplatin carboplatin and and oxaliplatin) oxaliplatin) in in the the therapy therapy of of solid solid neo- neo- plasms,plasms, there there is is considerable considerable interest interest in in the the development development of of more more efficient efficient metal-based metal-based antitumorantitumor agents agents