BioAtla to Present Phase 1 Evalstotug Trial Data Showing Clinical Benefit at 2024 ASCO Annual Meeting

BioAtla, Inc. has shared promising data concerning their novel anti-CTLA-4 agent, evalstotug (BA3071), which was studied in combination with nivolumab in advanced solid tumors. This announcement outlines pivotal findings from an ongoing Phase 1 study demonstrating substantial progression-free survival (PFS) and manageable safety profiles, potentially positioning evalstotug as a leading CTLA-4 antibody. Evalstotug has shown prolonged PFS of over ten months in patients who had previously failed PD1 treatments, with responses confirmed in melanoma and carcinoma patients.

The company plans to complete the Phase 1 dose-escalation study of evalstotug at a 1-gram dose, equivalent to 14.2 mg/kg for a 70 kg individual. A Phase 2 monotherapy study is ongoing, focusing on refractory melanoma and carcinoma patients. Additionally, BioAtla is enrolling patients in first-line combination therapy expansion cohorts, anticipating a readout in the second half of the year. They also plan a Phase 3 trial for first-line metastatic, unresectable BRAF-mutated melanoma, expected to begin in the latter half of 2024 following discussions with the FDA.

In the Phase 1 study, evalstotug was tested in doses ranging from 7 mg to 1 gram, administered every three weeks alongside 240 mg of nivolumab. The study involved 21 patients who had undergone a median of three prior systemic therapies and had all experienced anti-PD-1 therapy failures. Patients receiving 350 mg of evalstotug were able to tolerate more doses compared to historical data on ipilimumab or tremelimumab, with no dose reductions required. Notably, three patients successfully tolerated the first 1-gram dose, with clearance of the dose-limiting toxicity (DLT) observation period anticipated by early June. Population pharmacokinetic (PK) modeling suggests that a 1-gram dose will maintain adequate drug levels in over 98% of patients, potentially enhancing clinical benefits.

Safety data indicate that evalstotug is generally well-tolerated, with a relatively low incidence of immune-mediated adverse events (AEs). Four patients experienced Grade 3 treatment-emergent AEs, including two cases of immune-related AEs (diarrhea and diabetic ketoacidosis). Importantly, there were no Grade 4 or 5 treatment-related AEs observed, and only two patients discontinued treatment due to AEs. Among heavily pre-treated patients, clinical benefits were observed with evalstotug: three patients exhibited confirmed responses, including one complete response in cervical carcinoma, one partial response in gastroesophageal carcinoma, and one unconfirmed partial response in cutaneous melanoma. Additionally, the disease control rate was 52%, with some patients remaining progression-free for over a year.

BioAtla’s upcoming Phase 2 studies will further examine the efficacy and safety of evalstotug, both as a monotherapy and in combination with PD-1 inhibitors. The company anticipates that evalstotug, due to its unique conditionally active biologic (CAB) properties, will offer a differentiated tolerability profile and potentially become a best-in-class CTLA-4 antibody.

BioAtla continues to leverage its proprietary CAB technology to develop novel therapeutic candidates aimed at solid tumors. CAB antibodies are designed to be active specifically within the tumor microenvironment, offering enhanced targeting and reduced systemic toxicity. This approach not only improves safety but also broadens the patient population that may benefit from combination therapies. BioAtla's robust pipeline includes additional CAB programs currently in Phase 2 clinical testing and the first dual CAB bispecific T-cell engager antibody in Phase 1 development.

These advancements underscore BioAtla’s commitment to developing innovative cancer therapies that provide significant clinical benefits while minimizing adverse effects, potentially transforming treatment paradigms for various solid tumors.