Hybrid molecules, chemical entities with two or more pharmacophore domains, are widely investigated for their antiparasitic potential. First-in-class antimalarial hybrids were designed and tested against Plasmodium falciparum. Our multistep synthesis, initiated by a Mn(III)-mediated radical reaction, led to new hybrids containing both the pharmacophores of atovaquone (naphthoquinone) and artemisinin (endoperoxide) separated by a piperazine linker. With 2 or 3 asymmetric carbons, 4 to 8 theoretical configurational isomers were expected. For two of our 5 final products, chiral chromatography separated all isomers. 20 single isomers or stereoisomeric mixtures were obtained and tested against Plasmodium falciparum W2 and K1 chloroquine-resistant strains for their antiplasmodial activity and against HepG2 and CHO cells for their cytotoxicity. Antiplasmodial activity was better than those obtained for reference compound chloroquine for 15 compounds on PfW2 strain and 8 compounds on PfK1 strain. Hit compounds were identified among stereoisomer mixtures (12, IC50PfW2 = 0.489 μM, IC50PfK1 = 1.061 μM, CC50 HepG2 = 11.99 μM, CC50 CHO >125 μM) but also among several stereoisomers. These results suggest that hybrid compounds naphthoquinone/endoperoxide synthesized by adding two pharmacophores can lead to a synergistic effect.

Oxidative phosphorylation (OXPHOS), a major metabolic pathway in normal/differentiated cells is also active in tumors and a target for cancer drug development. Atovaquone, an FDA-approved antiprotozoal and OXPHOS inhibitor, blocks electron transport at mitochondrial Complex III resulting in an oxygen radical surge that triggers cancer cell death. Here, we examine mechanisms that attenuate the efficacy of atovaquone as an anti-cancer agent. First, we demonstrate that exposure to atovaquone causes DNA damage and loss of nuclear integrity in cancer cells. DNA damage by atovaquone does not activate cGAS-STING signaling, likely due to repressed cGAS expression in the cell lines tested. Instead, ATM/ATR signaling is activated in response to atovaquone. Recently, we demonstrated that oxidative and endoplasmic reticulum stress in atovaquone-treated cancer cells was associated with elevation in danger associated molecular patterns (DAMPs) corresponding to increased lysis by natural killer cells. Contrary to this immune activating effect, we now report that cancer cells also employ an immunosuppressive mechanism upon exposure to atovaquone. Specifically, we observed ATM/ATR-dependent increase in expression of PD-L1 on the cancer cells. Increase in PD-L1 required STAT1 signaling but was not regulated by IRF1, HIF1α or p53. Increase in PD-L1 was confirmed on peritoneal p53-/- ID8-F3 tumors growing in mice receiving atovaquone therapy. Combining atovaquone with anti-PD-L1 resulted in significant delay in tumor growth. Data from this study provides a mechanistic basis for PD-L1 elevation in tumors treated with atovaquone. Our studies support further development of atovaquone-anti-PD-L1 combination for the treatment of ovarian and other malignancies.

Babesiosis is a protozoan infection transmitted by the tick, Ixodes scapularis. The disease presentation varies from asymptomatic to fatal illness. Usually, severe illness occurs in asplenic and immunocompromised patients. In rare cases, the complication of splenic injury, including infarcts and rupture, has been observed in young individuals. We present the case of a middle-aged woman who presented with abdominal pain and fatigue. She was found to be febrile and hypotensive with thrombocytopenia, hemolytic anemia, and elevated transaminases. Imaging of the abdomen demonstrated multiple splenic infarcts. The patient denied a history of abdominal trauma and tick exposure. Autoimmune and infective endocarditis workup was negative. Subsequently, she tested positive for Babesia microti by polymerase chain reaction (PCR) test, and peripheral smear was remarkable for intracellular and extracellular ring forms consistent with Babesia with a parasitemia index of 1%. She tested negative for Lyme disease and anaplasmosis by enzyme-linked immunosorbent assay (ELISA) and PCR, respectively. She was started on atovaquone and azithromycin. On day 8 of hospitalization, she was transfused with one unit of packed red blood cells due to a hemoglobin level of 6.8 g/dL. Repeat parasitemia index on discharge was 0.01%. She was later discharged without further need for blood transfusions or surgical interventions. This case highlights the importance of considering babesiosis as a cause of acute splenic infarcts in endemic regions, even without reported exposure.

Babesiosis is a tick-borne intraerythrocytic protozoal infection endemic to the northeastern United States. Coinfection with other Ixodes-transmitted pathogens may occur due to shared vector exposure, although confirmed triple infection remains uncommon. Severe babesiosis, defined by parasitemia ≥10% or evidence of organ dysfunction, may present atypically in immunocompromised individuals. A 73-year-old man with end-stage renal disease on hemodialysis presented with two weeks of cyclic fevers, chills, and weakness after hiking in upstate New York. Physical examination revealed asterixis without rash, jaundice, or organomegaly. Laboratory evaluation demonstrated hemoglobin 6.9 g/dL, platelet count 124 K/µL, lactate dehydrogenase 709 U/L, and 13% parasitemia on peripheral smear. Polymerase chain reaction confirmed Babesia microti. Serologic testing revealed positive Lyme IgG and IgM antibodies and elevated Anaplasma phagocytophilum IgG titers. The patient was treated with azithromycin, atovaquone, and doxycycline, resulting in parasitemia clearance by hospital day 7 without exchange transfusion. Severe babesiosis with Ixodes-borne coinfection may occur without classic findings such as rash or hepatosplenomegaly, particularly in dialysis-dependent patients. Persistent fever in endemic regions despite doxycycline therapy should prompt evaluation for babesiosis. Early recognition and individualized management may prevent invasive interventions.

Familial thoracic aortic aneurysm and dissection (FTAAD), caused by the pathogenic Myh11 K1256del variant, is characterized by impaired aortic contractility; however, how reduced contractility predisposes the aorta to dissection remains incompletely understood. In this study, we performed a data-driven trans-omic upstream analysis using Genome Enhancer to identify key regulatory mechanisms in aortas from Myh11 K1256del mice under baseline conditions, without exposure to exogenous pathological stimuli. Transcriptome analysis revealed enrichment of genes related to smooth muscle contraction and regulation of myosin light chain phosphatase activity. Upstream computational analysis of regulatory regions identified nuclear factor of activated T cells 1 and lymphoid enhancer-binding factor 1 as major transcription factors, and further highlighted Rho-associated, coiled-coil-containing protein kinase 1 (ROCK1) as a predicted central regulator of the dysregulated transcriptional network. Druggability analysis suggested ROCK1 and the JunB proto-oncogene AP-1 transcription factor subunit as potential therapeutic targets. Furthermore, it predicted 51 candidate therapeutants, including atorvastatin, GSK-269962A, and atovaquone. These findings indicate that even in the absence of overt pathological stimulation, aortic tissue carrying the Myh11 K1256del variant exhibits a transcriptional program centered on ROCK signaling, which may prime the aorta for maladaptive responses to additional stress and may enhance susceptibility to dissection. This computational analysis requires experimental validation, but may provide a hypothesis-generating framework for development of preventive pharmacological interventions against FTAAD.

Here, we present the synthesis, characterization, and pharmacological evaluation of ruthenium complexes of broad-spectrum drug Atovaquone (ATV). Structure-activity relationships revealed key determinants for antiplasmodial activity, such as the importance of the oxidation state [Ru(III) versus Ru(II)] and of hydrophilic or lipophilic coligands. These complexes demonstrated broader activity against both asexual and sexual parasite stages than ATV. Due to this broader effect, complexes exhibited faster action in antiplasmodial activity than ATV. Ruthenium content from the complexes' treatment gradually and selectively accumulates in the parasite cell milieu. Efficacy was assessed in vivo against asexual and sexual stages. Complexes were capable of blocking parasite transmission from humans to insects, and this was achieved for both gametocytes and oocyst stages, while ATV solely blocked oocysts. This is the first example of metal complexes inhibiting both asexual and sexual parasites with similar potency, broadly expanding the therapeutic utility of metalladrugs in medicinal chemistry.

Toxoplasma gondii is a protozoan parasite capable of infecting most warm-blooded animals, including humans, and can cause severe disease in immunocompromised individuals and the developing fetus. Current treatments for toxoplasmosis are effective only against the acute stage of infection and have limited or no activity against the latent bradyzoite stage found within tissue cysts. The mitochondrion of T. gondii is a validated drug target, and the clinically used drug atovaquone acts by inhibiting the mitochondrial electron transport chain (ETC) at the coenzyme Q:cytochrome c oxidoreductase ( bc 1 complex). In this study, we evaluate two legacy 4(1 H )-quinolones: ICI 56,780 and WR 243246, previously shown to inhibit the Plasmodium falciparum bc 1 complex, for their efficacy against T. gondii . Both compounds inhibit tachyzoite growth with low-nanomolar EC₅₀ values and disrupt parasite mitochondrial function by blocking cytochrome c reduction and collapsing the mitochondrial membrane potential. Notably, ICI 56,780 protects mice from lethal infection with type I RH tachyzoites. Importantly, ICI 56,780 also exhibits potent activity against chronic-stage parasites, reducing cyst size and bradyzoite viability in vitro and showing low-nanomolar EC₅₀ values against in vivo -derived bradyzoites. In mice chronically infected with T. gondii , treatment with ICI 56,780 significantly decreases brain cyst burden. Although these 4(1 H )-quinolones display some pharmacokinetic limitations, our findings highlight their potential as promising chemotypes active against both acute and chronic stages of T. gondii and provide a framework for future medicinal chemistry efforts to improve drug-like properties while preserving or enhancing anti-bradyzoite activity.

Human granulocytic anaplasmosis is an emerging tick-borne illness caused by Anaplasma phagocytophilum and transmitted by Ixodes ticks. Clinical manifestations are often nonspecific, including fever, malaise, and cytopenias, which can delay recognition and treatment. Although thrombocytopenia is common in human granulocytic anaplasmosis (HGA), profound thrombocytopenia is rarely described, and cardiac conduction abnormalities remain infrequently reported. We describe a 73-year-old woman in New England who developed fever, somnolence, acute kidney injury, transaminitis, a platelet nadir of 12 × 10 9 / L ( 168 - 382 × 10 9 / L ) , and a new right bundle branch block (RBBB) with modest troponin elevation. Peripheral smear revealed Döhle bodies, vacuolated neutrophils, and giant platelets. Respiratory viral panel and blood cultures were negative. Polymerase chain reaction (PCR) confirmed A. phagocytophilum. The patient was initially treated empirically with atovaquone and azithromycin for presumed babesiosis, but therapy was narrowed to doxycycline with rapid recovery of symptoms and normalization of laboratory abnormalities. No echocardiogram or repeat electrocardiogram was performed during hospitalization despite the new conduction abnormality and elevated troponin, limiting conclusions regarding causality. This case underscores the need for heightened clinical suspicion in endemic regions, highlights an unusual severity of thrombocytopenia, and raises questions regarding potential cardiac involvement after the incidental finding of a new right bundle branch block.

Babesia microti is a tick-borne apicomplexan parasite of emerging public health importance, particularly in the northeastern United States. Current medications (e.g., atovaquone, azithromycin, clindamycin, and quinine) display limited efficacy and frequent adverse effects, underscoring the urgent need for safer and more potent therapies. In this study, we harnessed a computational drug design pipeline to develop novel sanguinarine derivatives targeting B. microti lactate dehydrogenase (BmLDH)-an essential enzyme for parasite metabolism. We first modified the sanguinarine scaffold to create eight derivatives, followed by structural geometry optimization in Gaussian, molecular docking, and Uni-GBSA scoring to identify top binders. Next, ADMET and drug-likeness analyses demonstrated that these derivatives met essential pharmacokinetic criteria. To further characterize these compounds, DFT calculations were performed to elucidate key electronic and quantum chemical descriptors such as HOMO-LUMO energies, ionization potentials, electron affinities, and electrophilicity indices. The molecular docking docking study reveals Ligand 02 and 04 showed highest affinity with -10.2 and -10.4 kcal mol respectively than the reference compound (-6.60 kcal/mol). Additionally, the Uni-GBSA score also support the binding strength of our selected ligands. Finally, MD simulations revealed stable binding performance of the selected three complexes (Ligand 02, 04, and standard/Diminazene), as evidenced by RMSD, RMSF, Rg, MM-PBSA, PCA, and DCCM. Two derivatives (ligands 02 and 04) showed notably high binding affinities and robust dynamic stability, surpassing the standard diminazene in key metrics. These findings highlight the potential clinical impact of modified sanguinarine derivatives-offering a compelling alternative to current treatments constrained by limited efficacy and adverse effects. This in silico study confirms that our investigated molecules may provide a new opportunity for discovering anti-parasitic drugs against Babesia microti. However, further experimental validation and clinical development are required.

Primary prophylaxis of Pneumocystis jirovecii pneumonia (PCP) in people with HIV (PWH) and CD4+ counts <200 cells/µL using trimethoprim/sulfamethoxazole (TMP-SMX) is highly effective but often poorly tolerated. Alternative agents may have limited efficacy or availability. Although rezafungin demonstrated PCP protection comparable to TMP-SMX in animal models, human data are limited to the ongoing ReSPECT trial, and evidence in PWH is lacking. We report the first use of rezafungin as PCP prophylaxis in a PWH. A 43-year-old man presenting with AIDS (HIV-RNA 8.48 × 10[6] copies/mL; CD4+ 20 cells/µL) was admitted with disseminated tuberculosis and multiple bowel perforations requiring urgent surgery. The postoperative course was marked by infectious and surgical complications. Antitubercular therapy and TMP-SMX prophylaxis were initiated postoperatively, followed by antiretroviral therapy (ART). Later, TMP-SMX was discontinued due to hypersensitivity. Because drug-drug interactions precluded atovaquone or dapsone and pentamidine was unavailable, rezafungin was started. No adverse events or fungal breakthrough infections occurred despite abdominal complications. Further data are needed to determine whether rezafungin represents a viable prophylactic option when standard agents are contraindicated or unavailable.

The efficacy of immunogenic photodynamic therapy (PDT) is critically limited by the inadequate tumor accumulation of photosensitizers and the resultant hypoxia in the tumor microenvironment. To address these challenges, we report a multifunctional nano-photosensitizer (TACR) constructed via a one-step self-assembly of a mitochondrial-targeting photosensitizer (TPP-Ppa), the hypoxia-relief agents (catalase and atovaquone), and a tumor-targeting ligand (RGD-PEG-BSA). TACR achieves sequential active targeting to tumor tissues and mitochondria. Crucially, it orchestrates a dual-path oxygen-economizing strategy: catalase decomposes endogenous H2O2 to generate O2, while atovaquone inhibits mitochondrial respiration to reduce oxygen consumption. This localized oxygen replenishment significantly enhances the production of cytotoxic singlet oxygen by TPP-Ppa upon 660 nm irradiation, leading to potent tumor cell killing and immunogenic cell death (ICD). The elicited ICD promotes dendritic cell maturation and cytotoxic T lymphocyte activation, effectively reversing the immunosuppressive tumor microenvironment. In a murine model of triple-negative breast cancer, TACR-mediated PDT synergized with α-PD-L1 checkpoint blockade, achieving robust inhibition of both primary and distant tumor growth. This work presents a rational design of an intelligent nanoplatform that simultaneously overcomes the key barriers in PDT and effectively harnesses the immune system for combinatorial cancer therapy. STATEMENT OF SIGNIFICANCE: To address the challenges of hypoxia, immunosuppression, and metastasis in triple-negative breast cancer, a cascade-targeting and self-oxygenating nano-photosensitizer (TACR) was developed. It alleviates tumor hypoxia through a dual-action mechanism, enhancing photodynamic therapy efficacy while achieving precise tumor and mitochondrial accumulation. TACR-mediated photodynamic therapy induces immunogenic cell death and remodels the tumor microenvironment. In combination with α-PD-L1 immune checkpoint blockade, it elicits a systemic antitumor immune response, effectively suppressing both primary and distant tumors.

Epidermal growth factor receptor (EGFR) is overexpressed in most triple-negative breast cancer (TNBC) patients with poor prognosis; however, the therapeutic benefit of EGFR inhibitors (EGFRi) in breast cancer remains limited. In this study, we found poor response to EGFRi in TNBC was related to oxidative phosphorylation (OXPHOS) and breast cancer stem cells (BCSCs), and demonstrated that TDP43 (TAR DNA-binding protein 43) expression is positively correlated with non-response to EGFR tyrosine kinase inhibitors (EGFR-TKIs). TDP43 knockdown significantly enhances EGFR-TKI sensitivity and decreases EGFR-TKI resistance. Mechanistically, TDP43, a DNA/RNA-binding protein predominantly localized to the nucleus, translocates to mitochondria upon EGFR-TKI stimulation. The increased mitochondrial localization promotes OXPHOS, thereby enriching BCSCs and contributing to EGFR-TKI resistance. Inhibiting TDP43 expression or using our newly identified TDP43 inhibitor, atovaquone, suppresses OXPHOS and reduces EGFR-TKI resistance. Overall, our research identified TDP43 as a key regulator of EGFR-TKI sensitivity and resistance, and offers new therapeutic targets and promising application perspectives in TNBC.