Scalable preparation and differential pharmacologic and toxicologic profiles of primaquine enantiomers

  • Antimicrob Agents Chemother. 2014 Aug;58(8):4737-44. doi: 10.1128/AAC.02674-13.
N P Dhammika Nanayakkara  1 ,  Babu L Tekwani  2 ,  H M T Bandara Herath  3 ,  Rajnish Sahu  3 ,  Montip Gettayacamin  4 ,  Anchalee Tungtaeng  4 ,  Yvonne van Gessel  4 ,  Paul Baresel  5 ,  Kristina S Wickham  5 ,  Marilyn S Bartlett  6 ,  Frank R Fronczek  7 ,  Victor Melendez  8 ,  Colin Ohrt  8 ,  Gregory A Reichard  8 ,  James D McChesney  9 ,  Rosemary Rochford  5 ,  Larry A Walker  2
Affiliations
  • 1. National Center for Natural Products Research, Research Institute of Pharmaceutical Sciences, University of Mississippi, University, Mississippi, USA [email protected].
  • 2. National Center for Natural Products Research, Research Institute of Pharmaceutical Sciences, University of Mississippi, University, Mississippi, USA Department of Pharmacology, University of Mississippi, University, Mississippi, USA.
  • 3. National Center for Natural Products Research, Research Institute of Pharmaceutical Sciences, University of Mississippi, University, Mississippi, USA.
  • 4. Department of Veterinary Medicine, U.S. Army Medical Component, Armed Forces Research Institute of Medical Sciences (AFRIMS), Bangkok, Thailand.
  • 5. Department of Microbiology and Immunology, SUNY Upstate Medical University, Syracuse, New York, USA.
  • 6. Department of Pathology and Laboratory Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA.
  • 7. Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana, USA.
  • 8. Department of Experimental Therapeutics, Walter Reed Army Institute of Research, Silver Spring, Maryland, USA.
  • 9. Ironstone Separations, Inc., Etta, Mississippi, USA.
PMID: 24913163 DOI: 10.1128/AAC.02674-13
Abstract

Hematotoxicity in individuals genetically deficient in glucose-6-phosphate dehydrogenase (G6PD) activity is the major limitation of primaquine (PQ), the only antimalarial drug in clinical use for treatment of relapsing Plasmodium vivax malaria. PQ is currently clinically used in its racemic form. A scalable procedure was developed to resolve racemic PQ, thus providing pure enantiomers for the first time for detailed preclinical evaluation and potentially for clinical use. These enantiomers were compared for antiparasitic activity using several mouse models and also for general and hematological toxicities in mice and dogs. (+)-(S)-PQ showed better suppressive and causal prophylactic activity than (-)-(R)-PQ in mice infected with Plasmodium berghei. Similarly, (+)-(S)-PQ was a more potent suppressive agent than (-)-(R)-PQ in a mouse model of Pneumocystis carinii pneumonia. However, at higher doses, (+)-(S)-PQ also showed more systemic toxicity for mice. In beagle dogs, (+)-(S)-PQ caused more methemoglobinemia and was toxic at 5 mg/kg of body weight/day given orally for 3 days, while (-)-(R)-PQ was well tolerated. In a novel mouse model of hemolytic anemia associated with human G6PD deficiency, it was also demonstrated that (-)-(R)-PQ was less hemolytic than (+)-(S)-PQ for the G6PD-deficient human red cells engrafted in the NOD-SCID mice. All these data suggest that while (+)-(S)-PQ shows greater potency in terms of antiparasitic efficacy in rodents, it is also more hematotoxic than (-)-(R)-PQ in mice and dogs. Activity and toxicity differences of PQ enantiomers in different species can be attributed to their different pharmacokinetic and metabolic profiles. Taken together, these studies suggest that (-)-(R)-PQ may have a better safety margin than the racemate in human.

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