Malaria, caused by Plasmodium falciparum, remains a major global health challenge, with an estimated 263 million new infections and 597,000 deaths annually. Increasing resistance to current antimalarial drugs underscores the urgent need for new therapeutics that target novel pathways in the parasite. We previously reported a novel class of β-carboline antimalarials, exemplified by PRC1584, which demonstrated a favorable oral pharmacokinetic profile, in vivo efficacy in Plasmodium berghei-infected mice, and no cross-resistance with other antimalarials in various P. falciparum strains. In this study, we demonstrate that PRC1584 exhibits a high resistance barrier and retains potent activity against fresh Ugandan P. falciparum isolates. PRC1584, along with its more potent analog PRC1697, demonstrated strong in vitro potency against both actively proliferating ring stages and dihydroartemisinin-induced dormant stages. Additionally, our study demonstrated that PfKelch13-C580Y mutation was associated with an increased susceptibility to PRC1584, whereas PfKelch13-R549T and Pfcoronin-R100 K-E107V mutations were not associated with this effect. These findings underscore the therapeutic potential of this new “irresistible” compound class, support a possible novel mechanism of action, and suggest the future development of novel ACTs active against resistant parasites by targeting DHA dormancy, an essential survival mechanism of P. falciparum.
Reagan S Haney, Joshua H Butler, Lyric A Wardlaw, Emilio F Merino, Victoria Mendiola, Caitlin A Cooper, Jopaul Mathew, Patrick K Tumwebaze, Philip J Rosenthal, Roland A Cooper, Dennis E Kyle, Zaira Rizopoulos, Delphine Baud, Stephen Brand, Maxim Totrov, Paul R Carlier, Maria Belen Cassera. ACS Infect Dis. 2025 Oct 17. doi: 10.1021/acsinfecdis.5c00714.
Buprenorphine is an opioid used for pain management in veterinary medicine but which requires frequent dosing to maintain therapeutic levels. Sustained-release buprenorphine (BSR) formulations can overcome this limitation, but genera- or species-specific studies that determine the time profiles of buprenorphine after dosing are sparse for NHPs. The objective of this study was to determine the plasma buprenorphine concentrations for 72 hours after a single subcutaneous administration of 0.2 mg/kg BSR or Ethiqa XR (EXR), an FDA-indexed, extended-release buprenorphine formulation, in owl monkeys. Blood samples were taken before and at 1, 4, 8, 24, 48, and 72 hours after administering either formulation to determine plasma buprenorphine concentrations. Clinical observations were also performed. A single 0.2 mg/kg dose of BSR and EXR raised plasma buprenorphine concentrations above the hypothesized therapeutic threshold for NHPs of 0.1 ng/mL within 1 hour of administration and maintained these levels for at least 72 hours. However, this dose did not sustain buprenorphine concentrations above the human efficacy threshold of 0.5 ng/mL for 72 hours. A subsequent study evaluated a single dose of 0.3 mg/kg EXR to determine whether this dose sustained plasma buprenorphine levels >0.5 ng/mL for 72 hours. Most owl monkeys reached this threshold and maintained plasma buprenorphine concentrations >0.5 ng/mL with this dose, albeit with increased side effects, including sedation and ptyalism. Injection site reactions were not observed in any animals during any study. In sum, this work indicates that a single subcutaneous dose of 0.2 mg/kg BSR or EXR can maintain buprenorphine above the hypothesized therapeutic threshold for NHPs of 0.1 ng/mL for 72 hours, but the EXR dose must be increased to reach the human efficacy threshold for 72 hours in owl monkeys.
Taylor A Sheridan, Celia L Saney, Amadis Vivas, Magdalena A Argomaniz, Wayne T Cheng, Tia S Freeman, David J Anderson, Saniya S Sabnis, Sarah Gayle Roberson, Cheryl Paladino, Matthew Doster, Anna Santos, Christopher A Reilly, Joseph E Rower, Gina A Kim, Mary Ann McCrackin, Chester J Joyner. J Am Assoc Lab Anim Sci. 2025 Sep 1:1-7. doi: 10.30802/AALAS-JAALAS-25-059.
Tetrahydro-β-carboline 1 (MMV008138) controls growth of asexual blood-stage Plasmodium falciparum by inhibiting IspD, an enzyme in the MEP pathway for synthesis of a critical metabolite, isopentenyl pyrophosphate (IPP). We have previously investigated the structure activity relationship (SAR) of three of its four rings (B, C, and D). In this report we investigate the SAR of the benzo- (i.e. A-ring) of 1, with the goal of increasing its in vitro antimalarial potency and metabolic stability. As in our previous studies of the B- and C-ring substitution, extreme sensitivity to substitution was also seen in the benzo-ring. In total, 19 benzo-ring substitution variants of 1 were prepared. When tested against multidrug-resistant (Dd2 strain) P. falciparum, only three derivatives (20a, c, d) possessed asexual blood stage (ABS) activity with EC50 values within 3-fold of the parent. As hoped, one analog (20c) showed a marked improvement in microsomal stability. However, this improvement unfortunately did not improve plasma exposure relative to 1, and did not lead to oral efficacy in a mouse model of malaria.
Maryam Ghavami, Haibo Li, Lixuan Liu, Joshua H Butler, Sha Ding, Grant J Butschek, Reagan S Haney, R McAlister Council-Troche, R Justin Grams, Emilio F Merino, Jennifer M Davis, Maxim Totrov, Maria B Cassera, Paul R Carlier. RSC Med Chem. 2025 Aug 15. doi: 10.1039/d5md00439j.
OSMAC (one strain many compounds) provides a convenient strategy to produce chemically diverse and novel natural products. In the study, the application of an OSMAC approach on a fungus Penicillium citrinum YSC-1 isolated from a medicinal plant Chloranthus japonicus, using different culture media, led to the isolation and identification of seven new spirooxindole alkaloids penicitrimicins A-G (1-7) with a rare 6/5/5/6/6 polycyclic skeleton, along with two known compounds (8-9). The new structures were characterized based on the comprehensive spectroscopic analyses, including 1D, 2D NMR and HRESIMS data. The absolute configurations of compounds 1-7 were determined by modified Mosher ester methodology, PGME derivatization, X-ray crystallographic analysis, and quantum chemical calculations. Biological evaluation revealed that these spirooxindole alkaloids exhibited good biocompatibility (<5 % hemolysis and > 80 % cell viability) while displaying obvious antimalarial activity against Plasmodium falciparum Dd2 strain, with EC50 values spanning 0.9-2.4 μM. Furthermore, stage-specific assays revealed that compound 5 displayed significant inhibitory effects on the developmental transition of asexual blood-stage parasites, effectively blocking their progression to subsequent lifecycle stages.
New test protocol can detect low levels of Trypanosoma cruzi, the parasite that causes Chagas disease
Researchers at the University of Georgia’s Center for Tropical and Emerging Global Diseases have developed the first test to determine whether treatment for Chagas disease was effective.
An estimated 6 million to 8 million people worldwide are infected with Trypanosoma cruzi, the parasite that causes Chagas disease.
“Currently during drug trials, we can only determine if a drug fails,” said Rick Tarleton, Regents’ Professor in the UGA Franklin College of Arts and Sciences. “A test of cure can indicate if a drug succeeds in clearing the infection.”
Rick Tarleton of the Center for Tropical and Emerging Global Diseases
Part of the problem in determining if T. cruzi infection is cured by treatment is that the immune system is often very good at controlling the infection. Current tests are not sensitive enough to detect low levels of parasites.
“If you have a cup a tea with a little bit of tea leaf in it you may not get a tea leaf in every sip,” Tarleton said. “When there are so few parasites in the blood stream, it decreases the chances that a blood draw will contain any.
“We’ve taken two samples from the same individual at the same time—one sample tests positive, and the other tests negative. Which is right?”
Thousands die from Chagas each year
Chagas disease kills more than 10,000 people every year, mainly in Central and South America. But it is also a concern in the United States, where the Centers for Disease Control and Prevention estimates there are 280,000 people living with this disease.
And it’s not only humans that suffer from this disease. Many mammals, including wildlife and dogs, can also become infected.
The Tarleton group conducted large-scale PCR testing of samples from naturally infected macaque monkeys, dogs and humans. The team also fragmented the DNA to more evenly distribute it within the sample. Standard PCR testing doesn’t fragment DNA.
“If we go back to Rick’s tea leaf example, it’s like taking the whole tea leaf, breaking it up into tiny bits and then stirring the tea before taking a sip,” said Brooke White, lead researcher of the study. “This increases the chances of detecting DNA.”
New test accurately detects parasite infection in monkeys, dogs and humans
The naturally infected macaques were monitored over 12 months with monthly blood tests. A subset also had blood samples drawn seven times over four weeks. In addition to the exhaustive PCR testing, the researchers grew T. cruzi cultures from the blood samples, which confirmed that the new protocol accurately detects infection even when the parasite number is very low.
“Since the macaques acquired the infection in the same way as humans and dogs and their disease progression is the same, we are confident that this test will work in other species,” said Tarleton.
Collaborators at Texas A&M and in Argentina also provided naturally infected dog and human samples, respectively. The researchers saw similar results to the macaques.
A need for better drug treatment for Chagas disease
There is a need for new drug treatments for Chagas disease. But without a true test of cure, researchers only know what does not work. While the new protocol is effective, the researchers noted that it is also labor intensive and time consuming, which translates into being costly.
As part of the study, the researchers sought out technologies that could make the process faster and cheaper.
“This test of cure is a real game changer for drug treatment studies,” said White. “We are already working with other research groups in hopes of creating a quicker and cheaper method of testing parasite load in their drug treatment studies in macaques, dogs and humans.”
The researchers began collaborating with Countable Labs whose new technology allows for larger samples to be assayed faster. Reducing costs and increasing efficiency makes it much more likely for this test to be used in a clinical setting.
“Our goal now is to move this test out of the research lab and into a clinical diagnostic lab where it will be widely accessible for detecting human and dog infections and tracking treatment outcomes,” said Tarleton.
The Trypanosoma brucei group of parasites causes Nagana in cattle and human African trypanosomiasis, or sleeping sickness, in humans. Current drugs against these parasites have severe toxicity, vaccines are not available, and development of drug resistance makes finding new chemotherapeutic targets imperative. Ion channels, which are involved in several biological processes, are targets of many therapeutically useful agents, and they remain significantly underexplored as therapeutic targets in parasites. Here, we report the presence of a voltage gated Ca2+ channel (VGCC, TbCav), which is localized in the flagellar plasma membrane (PM) of T. brucei and is essential for proliferation of both bloodstream (BSF) and procyclic forms (PCF) of the parasite. TbCaV is a single subunit channel capable of transporting Ca2+ when expressed in mutant yeast lacking PM Ca2+ channels or in HEK293T cells. Through the virtual screening of a commercial chemical library using dynamic ensembles of various conformations of TbCav and associated docking analyses, several inhibitors of TbCav were discovered. As pharmacological validation of the essential roles of TbCav, these compounds were shown to inhibit T. brucei growth with the most potent agent, N-(7-nitro-2,1,3-benzoxadiazol-4-yl) acetamide (NBD-A), exhibiting an EC50 of 25 ± 3 nM and no cytotoxicity in Vero cells possessing related channels. Thus, such studies constitute pharmacological validation of TbCav as a viable therapeutic target of T. brucei.
Artemisinin combination therapies (ACTs) are critical components of malaria control worldwide. Alarmingly, ACTs have begun to fail, owing to the rise in artemisinin resistance. Thus, there is an urgent need for an expanded set of novel antimalarials to generate new combination therapies. Herein, we have identified a 1,2,4-triazole-containing carboxamide scaffold that, through scaffold hopping efforts, resulted in a nanomolar potent deuterated picolinamide (110). The lead compound of this class (110) displays moderate aqueous solubility (13.4 μM) and metabolic stability (CLintapp HLM 17.3 μL/min/mg) in vitro, as well as moderate oral bioavailability (%F 16.2) in invivo pharmacokinetic studies. Compound 110 also displayed activity against various P. falciparum isolates with different genetic backgrounds and a slow-to-moderate rate of killing (average parasite reduction ratio 2.4), making the series appealing for further development.
Alicia Wagner, Roger Trombley, Maris Podgurski, Anthony A Ruberto, Meng Cui, Caitlin A Cooper, William E Long, Gia-Bao Nguyen, Adriana A Marin, Sarah Lee Mai, Franco Lombardo, Steven P Maher, Dennis E Kyle, Roman Manetsch.Eur J Med Chem. 2025 Mar 28:291:117572. doi: 10.1016/j.ejmech.2025.117572.
Half the world’s population is at risk of developing a malaria infection, which is caused by parasites of the genus Plasmodium. Currently, resistance has been identified to all clinically available antimalarials, highlighting an urgent need to develop novel compounds and better understand common mechanisms of resistance. We previously identified a novel tetrahydro-β-carboline compound, PRC1590, which potently kills the malaria parasite. To better understand its mechanism of action, we selected for and characterized resistance to PRC1590 in Plasmodium falciparum. Through in vitro selection of resistance to PRC1590, we have identified that a single-nucleotide polymorphism on the parasite’s multidrug resistance protein 1 (PfMDR1 G293V) mediates resistance to PRC1590. This mutation results in stereospecific resistance and sensitizes parasites to other antimalarials, such as mefloquine, quinine, and MMV019017. Intraerythrocytic asexual stage specificity assays have revealed that PRC1590 is most potent during the trophozoite stage when the parasite forms a single digestive vacuole (DV) and actively digests hemoglobin. Moreover, fluorescence microscopy revealed that PRC1590 disrupts the function of the DV, indicating a potential molecular target associated with this organelle. Our findings mark a significant step in understanding the mechanism of resistance and the mode of action of this emerging class of antimalarials. In addition, our results suggest a potential link between resistance mediated by PfMDR1 and PRC1590’s molecular target. This research underscores the pressing need for future research aimed at investigating the intricate relationship between a compound’s chemical scaffold, molecular target, and resistance mutations associated with PfMDR1.
Emily K Bremers, Joshua H Butler, Leticia S Do Amaral, Emilio F Merino, Hanan Almolhim, Bo Zhou, Rodrigo P Baptista, Maxim Totrov, Paul R Carlier, Maria Belen Cassera. ACS Infect Dis. 2025 Jan 14. doi: 10.1021/acsinfecdis.4c01001.
Calophyllum tomentosum belonging to Clusiaceae family is an Indian medicinal plant used as folklore medicine to cure various kinds of diseases reported in Ayurveda, and the leaves of the plant are also used as an active ingredient for the preparation of a botanical medicine known as ‘Punnaga’, ‘Surapunnaga’ and ‘Tamoil’ among other common names. Chemical profiling of the methanol extract of the defatted leaf revealed the presence of amentoflavone as one of the constituents along with coumarins, terpenoids, steroids, and apetalic acids. Structural determination of these amentoflavone has been conducted by chemical, spectral, and spectrometric methods in comparison with spectral values available in the literature and confirmed by a single crystal X-ray diffraction study. Amentoflavone (1) and its derivative (2-5) tested to check the efficacy of anti-malarial activity against Plasmodium falciparum. Amongst them, only tetra methoxy amentoflavone, (2) exhibited moderate anti-malarial activity with IC50 value 1.99 ± 0.42 µM against Plasmodium falciparum in comparison with artemisinin as control, whereas the other products possessed almost negligible activity although their structural skeletons are identical with little variation of number and nature of substituents. The structure activity relationship (SAR) of the active constituent and its derivatives is reported herein.
Ajoy Kumar Bauri, Joshua H Butler, Maria B Cassera, Sabine Foro. Chem Biodivers. 2024 Oct 14:e202401576. doi: 10.1002/cbdv.202401576.
A systems biology approach for antimalarial drug discovery.
We report the discovery of MED6-189, an analog of the kalihinol family of isocyanoterpene natural products that is effective against drug-sensitive and drug-resistant Plasmodium falciparum strains, blocking both asexual replication and sexual differentiation. In vivo studies using a humanized mouse model of malaria confirm strong efficacy of the compound in animals with no apparent hemolytic activity or toxicity. Complementary chemical, molecular, and genomics analyses revealed that MED6-189 targets the parasite apicoplast and acts by inhibiting lipid biogenesis and cellular trafficking. Genetic analyses revealed that a mutation in PfSec13, which encodes a component of the parasite secretory machinery, reduced susceptibility to the drug. Its high potency, excellent therapeutic profile, and distinctive mode of action make MED6-189 an excellent addition to the antimalarial drug pipeline.
Z Chahine, S Abel, T Hollin, G L Barnes, J H Chung, M E Daub, I Renard, J Y Choi, P Vydyam, A Pal, M Alba-Argomaniz, C A S Banks, J Kirkwood, A Saraf, I Camino, P Castaneda, M C Cuevas, J De Mercado-Arnanz, E Fernandez-Alvaro, A Garcia-Perez, N Ibarz, S Viera-Morilla, J Prudhomme, C J Joyner, A K Bei, L Florens, C Ben Mamoun, C D Vanderwal, K G Le Roch. Science. 2024 Sep 27;385(6716):eadm7966. doi: 10.1126/science.adm7966.
