Work from my laboratory has focused primarily on identifying new antiparasitic drug candidates. Our early studies at Ohio State explored the protein tubulin as a target for antileishmanial and antitrypanosomal drug discovery [1-3]. Through a medicinal chemistry optimization program, we synthesized a series of oryzalin analogs and discovered that the addition of an aryl ring to the N1 position of oryzalin resulted in compounds with selective activity against Leishmania tubulin and potent effects on Leishmania and African trypanosome parasites in vitro. To my knowledge, our dinitroaniline compounds are the only known molecules with selective antitubulin antiparasitic activity that has been verified on the protein level with purified parasite tubulin and at the cellular level as indicated by cell cycle analysis. Further study of these selective antiparasitic antitubulin agents was ultimately discontinued due to their metabolic instability [4]. Our lab also conducted hit-to-lead followed by lead optimization chemistry on a dihydroquinoline compound emerging from a T. brucei screen conducted by the World Health Organization [5]. Our lab prepared numerous analogs of this hit possessing nanomolar in vitro potency against African trypanosomes with three orders of magnitude selectivity; three compounds were identified by our collaborators at the Swiss Tropical Institute that cured trypanosome infections in mice when administered by the intraperitoneal route [6]. In addition to carrying out synthetic medicinal chemistry on this class of molecules, my lab conducted mechanistic studies that led to the conclusion that the trypanocidal dihydroquinolines exert their antiparasitic effects by forming a quinone imine species that takes part in redox cycling in T. brucei, increasing oxidative stress on the trypanosome [5, 7]. With the approval of fexinidazole for use against African trypanosomiasis, our focus on drug development for human African trypanosomiasis has diminished in recent years.
Through collaborations made possible by our lab’s participation in the Consortium for Parasitic Drug Development from 2001-2011, we performed in vitro testing of new candidates against Leishmania and the evaluation of promising in vivo candidates in a murine model of visceral leishmaniasis. We tested oral amphotericin B lipid-based formulations developed at the University of British Columbia and found that they were highly effective when given orally in our murine visceral leishmaniasis model [8, 9]. We have also worked extensively with a potent class of antileishmanial compounds known as arylimidamides (AIAs). AIAs, synthesized by Dr. David Boykin’s lab at Georgia State University, were inspired by pentamidine but show superior activity against intracellular parasites due to the lower pKa of the amidine groups in the former. Although the frontrunner AIA, DB766, and its bis-AIA analogs did not display a sufficient therapeutic window to advance to preclinical development [10, 11], the exceptional in vitro potency of the AIAs encouraged us to examine mono-AIAs, which retain activity against Leishmania both in vitro and in vivo and in general appear to be less toxic as a class in animals [12]. We also showed that DB766 and the antifungal azole posaconazole displayed moderate synergy when this combination was examined in a murine visceral leishmaniasis model and that the pharmacokinetics of the combination influences this interaction [13]. These observations drive our current antileishmanial drug discovery and design efforts with related molecules in collaboration with Dr. Michael Wang at the University of Kansas.
Through our interest in antikinetoplastid drug discovery and development, we have also been involved in the screening of several additional classes of antileishmanial compounds. These include quinazoline-2,4-diamines prepared at the University of South Florida [14, 15] as well as semisynthetic berberine derivatives [16] and cyanines prepared in our own lab [17]. We have also begun to evaluate topical drug delivery strategies in a murine cutaneous leishmaniasis model [18]. We remain motivated to discover and develop new therapeutic approaches against leishmaniasis and are also eager to identify new biological activities for molecules made and/or tested in our lab.
References
[1] K.A. Werbovetz, D.L. Sackett, D. Delfin, G. Bhattacharya, M. Salem, T. Obrzut, D. Rattendi, C. Bacchi, Selective antimicrotubule activity of N1-phenyl-3,5-dinitro-N4,N4-di-n-propylsulfanilamide (GB-II-5) against kinetoplastid parasites, Mol. Pharmacol., 64 (2003) 1325-1333.
[2] G. Bhattacharya, J. Herman, D. Delfin, M. Salem, T. Barszcz, M. Mollet, G. Riccio, R. Brun, K. Werbovetz, Synthesis and antitubulin activity of N1– and N4-substituted 3,5-dinitro sulfanilamides against African trypanosomes and Leishmania, J. Med. Chem., 47 (2004) 1823-1832.
[3] T. George, M. Endeshaw, R. Morgan, K. Mahasenan, D. Delfín, M. Mukherjee, A. Yakovich, J. Fotie, C. Li, K. Werbovetz, Synthesis, biological evaluation, and molecular modeling of 3,5-substituted-N1-phenyl-N4, N4-di-n-butylsulfanilamides as antikinetoplastid antimicrotubule agents, Bioorg. Med. Chem., 15 (2007) 6071-6079.
[4] T. George, J. Johnsamuel, D. Delfín, A. Yakovich, M. Mukherjee, M. Phelps, J. Dalton, D. Sackett, M. Kaiser, R. Brun, K. Werbovetz, Antikinetoplastid antimitotic activity and metabolic stability of dinitroaniline sulfonamides and benzamides, Bioorg. Med. Chem., 14 (2006) 5699-5710.
[5] J. Fotie, M. Kaiser, D. Delfin, J. Manley, C. Reid, J. Paris, T. Wenzler, L. Maes, K. Mahasenan, C. Li, K. Werbovetz, Antitrypanosomal activity of 1,2-dihydroquinolin-6-ols and their ester derivatives, J. Med. Chem., 53 (2010) 966-982.
[6] C. Reid, D. Patrick, S. He, J. Fotie, K. Premalatha, R. Tidwell, M. Wang, Q. Liu, P. Gershkovich, K. Wasan, T. Wenzler, R. Brun, K. Werbovetz, Synthesis and antitrypanosomal evaluation of derivatives of N-benzyl-1,2-dihydroquinolin-6-ols: effect of core substitutions and salt formation, Bioorg. Med. Chem., 19 (2011) 513-523.
[7] S. He, A. Dayton, P. Kuppusamy, K. Werbovetz, M. Drew, Induction of oxidative stress in Trypanosoma brucei by the antitrypanosomal dihydroquinoline OSU-40, Antimicrob. Agents Chemother., 56 (2012) 2428-2434.
[8] K. Wasan, E. Wasan, P. Gershkovich, X. Zhu, R. Tidwell, K. Werbovetz, J. Clement, S. Thornton, Highly effective oral amphotericin B formulation against murine visceral leishmaniasis, J. Infect. Dis., 200 (2009) 357-360.
[9] E. Wasan, P. Gershkovich, J. Zhao, X. Zhu, K. Werbovetz, R. Tidwell, J. Clement, S. Thornton, K. Wasan, A novel tropically stable oral amphotericin B formulation (iCo-010) exhibits efficacy against visceral leishmaniasis in a murine model., PLoS Negl. Trop. Dis., 4 (2010) e913.
[10] M. Wang, X. Zhu, A. Srivastava, Q. Liu, J. Sweat, T. Pandharkar, C. Stephens, E. Riccio, S. Mandal, R. Madhubala, R. Tidwell, W. Wilson, D. Boykin, J. Hall, D. Kyle, K. Werbovetz, Novel arylimidamides for the treatment of visceral leishmaniasis, Antimicrob. Agents Chemother., 54 (2010) 2507-2516.
[11] X. Zhu, Q. Liu, S. Yang, T. Parman, C. Green, J. Mirsalis, M. Soeiro, E. de Souza, C. da Silva, D. Batista, C. Stephens, M. Banerjee, A. Farahat, M. Munde, W. Wilson, D. Boykin, M. Wang, K. Werbovetz, Evaluation of arylimidamides DB1955 and DB1960 as candidates against visceral leishmaniasis and Chagas disease – in vivo efficacy, acute toxicity, pharmacokinetics and toxicology studies, Antimicrob. Agents Chemother., 56 (2012) 3690-3699.
[12] X. Zhu, A. Farahat, M. Mattamana, A. Joice, T. Pandharkar, E. Holt, M. Banerjee, J. Gragg, L. Hu, A. Kumar, S. Yang, M. Wang, D. Boykin, K. Werbovetz, Synthesis and pharmacological evaluation of mono-arylimidamides as antileishmanial agents, Bioorg. Med. Chem. Lett., 26 (2016) 2551-2556.
[13] A. Joice, S. Yang, A. Farahat, H. Meeds, M. Feng, J. Li, D. Boykin, M. Wang, K. Werbovetz, Antileishmanial efficacy and pharmacokinetics of DB766-azole combinations, Antimicrob. Agents Chemother., 62 (2018) e01129-17.
[14] K. Van Horn, X. Zhu, T. Pandharkar, S. Yang, B. Vesely, M. Vanaerschot, J.-C. Dujardin, S. Rijal, D. Kyle, M. Wang, K. Werbovetz, R. Manetsch, Antileishmanial activity of a series of N2,N4-disubstituted quinazoline-2,4-diamines, J. Med. Chem., 57 (2014) 5141-5156.
[15] X. Zhu, K. Van Horn, M. Barber, S. Yang, M.Z. Wang, R. Manetsch, K. Werbovetz, SAR refinement of antileishmanial N2,N4-disubstituted quinazoline-2,4-diamines, Bioorg. Med. Chem., 23 (2015) 5182-5189.
[16] M. Endeshaw, X. Zhu, S. He, T. Pandharkar, E. Cason, K. Mahasenan, H. Agarwal, C. Li, M. Munde, W. Wilson, M. Bahar, R. Doskotch, A. Kinghorn, M. Kaiser, R. Brun, M. Drew, K. Werbovetz, 8,8-Dialkyldihydroberberines with potent antiprotozoal activity, J. Nat. Prod., 76 (2013) 311-315.
[17] A. Abdelhameed, X. Liao, C. McElroy, A. Joice, L. Rakotondraibe, J. Li, C. Slebodnick, P. Guo, W. Wilson, K. Werbovetz, Synthesis and antileishmanial evaluation of thiazole orange analogs, Bioorg. Med. Chem. Lett., in press, doi.org/10.1016/j.bmcl.2019.126725.
[18] A. Nguyen, K. Yang, K. Bryant, J. Li, A. Joice, K. Werbovetz, R. Narayan, Microneedle-based delivery of amphotericin B for treatment of cutaneous leishmaniasis, Biomed. Microdevices, 21 (2019) 8.