60 Degrees’ Babesiosis Bid: First-in-Class Opportunity Hinges on Repurposed Drug with Unproven Mechanism and Scant Data

60 Degrees Pharmaceuticals Achieves Minimum Enrollment for Hospitalized Babesiosis Study

60 Degrees Pharmaceuticals has enrolled the minimum 24 patients required to trigger an interim analysis in its clinical study (NCT06207370) evaluating tafenoquine for severe babesiosis. The company expects to disclose the outcome of this interim analysis by October 6, 2026. Following the readout, 60 Degrees Pharmaceuticals plans to request a meeting with the U.S. Food and Drug Administration (FDA) to discuss the regulatory pathway for a potential New Drug Application (NDA) for tafenoquine in babesiosis, for which there is currently no FDA-approved treatment.

• The ongoing clinical trial, titled "Oral Tafenoquine Plus Standard of Care Versus Placebo Plus Standard of Care for Babesiosis," is a double-blind, randomized, multisite, placebo-controlled study. It is designed to assess the efficacy and safety of tafenoquine in treating severe babesiosis in hospitalized human patients across multiple U.S. sites, including Tufts Medical Center and Yale University.
• The study's Data Safety and Monitoring Board (DSMB) will conduct the interim analysis, focusing on the primary endpoint of time to sustained clinical recovery from babesiosis and the key secondary endpoint of time to molecular clearance of Babesia parasites. The DSMB has the authority to recommend early study halting if statistical significance is reached for the primary endpoint, or to suggest enrolling more patients or closing the study if significance is unlikely.
• Currently, tafenoquine is not FDA-approved for babesiosis but is approved for malaria prophylaxis in the United States under the product name ARAKODA® and in Australia as KODATEF®. Following the interim analysis, 60 Degrees Pharmaceuticals intends to engage with the FDA to discuss the data requirements for a potential supplemental NDA submission for tafenoquine in the treatment of babesiosis.

The Urgent Need for New Babesiosis Treatments

Current management of human babesiosis relies on two antimicrobial regimens—atovaquone plus azithromycin, or clindamycin plus quinine—that were never rationally designed against Babesia-specific biology but were instead repurposed from other apicomplexan indications. This reliance on off-target therapeutics has produced a treatment landscape marked by suboptimal efficacy, tolerability concerns, and an escalating resistance problem, particularly in the most vulnerable patient populations.

• Suboptimal efficacy and safety profile: Both standard regimens are associated with mild-to-severe adverse events, and the clindamycin/quinine combination carries a higher rate of adverse reactions than azithromycin/atovaquone, limiting tolerability especially in patients requiring extended courses.

• Rapid emergence of drug resistance: Resistance to atovaquone, azithromycin, and clindamycin is increasingly documented and has been directly implicated in relapsing disease, particularly among highly immunocompromised patients, underscoring the fragility of the current pharmacologic arsenal.

• High mortality and relapse in high-risk populations: Despite standard antimicrobial therapy, mortality can reach up to 20% in high-risk groups; patients with advanced age, asplenia, or other forms of immune compromise are prone to severe, prolonged, or relapsing disease that often demands extended treatment courses to achieve parasitemia clearance.

• Unresolved role of exchange transfusion: For severe cases, therapeutic exchange transfusion is sometimes used, but its mechanism of clinical benefit remains poorly understood, and numerous questions about its appropriate application persist.

• Narrow and stagnant drug pipeline: Despite ongoing screening efforts, only a limited number of compounds have advanced toward clinical applicability, reflecting a broader unmet need for drug discovery efforts tailored specifically to Babesia parasite biology rather than borrowed from other pathogens.

• Emerging but early-stage alternatives: Investigational options—including botanical-derived compounds (e.g., cryptolepine, artemisinin and its derivatives, baicalein) with in vitro inhibitory activity against B. duncani comparable to or exceeding quinine and clindamycin, and tafenoquine, which has demonstrated broad and potent antibabesial activity—represent promising but still preliminary avenues that have yet to be fully translated into clinical practice.

• Persistent research gaps: Further research is needed to clarify the pathogenesis of B. duncani infection and to define optimal, evidence-based treatment regimens, reinforcing the urgency for therapeutics designed from the ground up for Babesia-specific targets.

Designing the Tafenoquine Trial for Severe Babesiosis

A review of historical and recent trials for babesiosis reveals a diversity of study designs, model systems, and endpoints. These studies, ranging from veterinary field trials to preclinical pharmacokinetic and in vitro evaluations, provide a valuable evidence base for informing the design of future clinical trials in human babesiosis. Key parameters include the selection of appropriate animal models, relevant pharmacodynamic and clinical endpoints, and safety monitoring protocols.

Tafenoquine's Established Safety Profile Across Indications

Tafenoquine demonstrates a generally favorable safety and tolerability profile across multiple clinical studies, often comparable to that of primaquine. The selection of the single 300 mg dose for radical cure was supported by safety data from over 4,000 trial participants. The primary safety concern remains the risk of hemolysis in individuals with G6PD deficiency, necessitating mandatory pre-treatment screening.

• Comparative Safety Profile vs. Primaquine: In head-to-head comparisons, tafenoquine's safety is similar to or favorable against primaquine. A multicentre trial found fewer drug-related adverse events before day 42 in the tafenoquine group (22.2%) compared to the low-dose primaquine group (34.2%). Furthermore, a 2021 meta-analysis showed no significant difference in the risk of serious adverse events versus primaquine, and the Phase 3 GATHER trial found that hemoglobin decline in G6PD-normal patients did not differ significantly between tafenoquine and primaquine.

• Common and Notable Adverse Events: The most frequently reported adverse events are often gastrointestinal in nature, with one study noting significantly more such events in tafenoquine users (p ≤ 0.001). With prolonged exposure for chemoprophylaxis, an increased incidence of reversible, asymptomatic vortex keratopathy has been observed. A single, serious event of decreased macular sensitivity has also been reported in the literature.

• G6PD Deficiency and Hemolysis Risk: The most significant safety risk associated with tafenoquine is the potential for drug-induced acute hemolytic anemia in patients with G6PD deficiency. Severe hemolysis can lead to serious complications, including kidney damage. Consequently, regulatory authorities and the WHO mandate G6PD testing to exclude deficiency before administering tafenoquine. A 2025 implementation study confirmed the effectiveness of this strategy, showing 100% appropriate use according to G6PD status.

Tafenoquine's Babesiosis Bid: A New Frontier for an Established Drug

The upcoming interim analysis for tafenoquine in severe babesiosis marks a pivotal moment for 60 Degrees Pharmaceuticals and the broader infectious disease landscape. Babesiosis, a tick-borne parasitic infection, currently lacks any FDA-approved treatment, leaving clinicians to rely on off-label regimens that can be complicated by drug resistance and suboptimal outcomes, particularly in immunocompromised patients. Tafenoquine, an 8-aminoquinoline already approved for malaria, has demonstrated promising activity against Babesia species in both in vitro and in vivo models, and has shown utility in case reports of relapsing babesiosis.

Should the interim analysis prove positive, 60 Degrees Pharmaceuticals stands to gain a significant first-mover advantage in a growing market. This strategic repurposing of an existing drug not only accelerates development by leveraging known safety profiles but also diversifies the drug's commercial lifecycle. However, the path forward is not without its complexities. A primary concern is tafenoquine's known risk of hemolytic anemia in individuals with glucose-6-phosphate dehydrogenase (G6PD) deficiency. This necessitates mandatory G6PD screening prior to treatment, which could present logistical hurdles in various healthcare settings and potentially limit patient access. Furthermore, while tafenoquine shows promise, some evidence suggests its optimal efficacy in babesiosis may be as part of a combination therapy rather than monotherapy, a factor that could influence its broad clinical adoption and future development strategies. The drug's long half-life, while offering dosing convenience, also means that any adverse events would be prolonged, demanding rigorous patient selection and monitoring. Ultimately, a successful outcome could usher in a much-needed therapeutic option for a challenging disease, but careful consideration of its unique safety profile and optimal use will be paramount for widespread clinical integration.