Multiple refractory PD1 failure patients experienced prolonged progression free survival (10 months ongoing); confirmed responses observed in patients receiving evalstotug

High doses of evalstotug as either a monotherapy or in combination with PD1 are associated with manageable safety with relatively low incidence and severity of immune-mediated AEs allowing patients to continue treatment for extended intervals  

On track for completion of Phase 1 dose-escalation of evalstotug at 1 gram (14.2 mg/kg for a 70 kg person) and Phase 2 monotherapy study with multiple scans in refractory melanoma and carcinoma patients; ongoing enrollment in 1st line combination therapy expansion cohorts for 2H readout

A Phase 3 trial of evalstotug in first-line metastatic, unresectable BRAF-mutated melanoma is
anticipated to initiate in 2H of 2024 following planned FDA meeting

SAN DIEGO, May  23, 2024  (GLOBE NEWSWIRE) -- BioAtla, Inc. (Nasdaq: BCAB), a global clinical-stage biotechnology company focused on the development of Conditionally Active Biologic (CAB) antibody therapeutics for the treatment of solid tumors, today announced expanded data at an upcoming presentation entitled, "Phase 1 study of evalstotug (BA3071), an anti-CTLA-4 Conditionally Active Biologic, in combination with nivolumab in advanced solid tumors", demonstrating confirmed responses with a potentially differentiated tolerability profile with the Company's novel, conditionally active anti-CTLA-4 agent, evalstotug, in combination with anti-PD-1 therapy. The poster will be presented at the upcoming 2024 American Society of Clinical Oncology (ASCO) Annual Meeting at the McCormick Place Convention Center in Chicago, Illinois on Saturday, June 1, 2024.

"Given the emerging clinical profile observed, we believe evalstotug has the potential to be best-in-class CTLA-4 antibody and holds the promise to be used as often as a PD-1 inhibitor," said Jay M. Short, Ph.D., Chairman, Chief Executive Officer and co-founder of BioAtla, Inc. "Strikingly, we have observed prolonged PFS of greater than 10 months and confirmed responses at high doses (350 mg), of evalstotug, suggesting increased exposure of CTLA-4 blockade in combination with PD-1 inhibition drives clinical benefit. We continue to enroll in the Phase 2 first-line melanoma and mutated NSCLC combination cohorts at the 700 mg flat dose and we anticipate moving to the 1 gram flat dose in June following clearance of the DLT observation period and remain on track for monotherapy and combination data readouts later this year. We anticipate enabling a Phase 3 trial of evalstotug in first-line metastatic or unresectable BRAF-mutated melanoma in the second half of this year.

Data highlights from poster include:

• A Phase 1 dose-escalation study evaluated evalstotug (7 mg – 1 g Q3W) in combination with nivolumab (240 mg), conducted in 21 patients

  • Data cut of March 29, 2024 unless otherwise specified

  • Patients received a median of 3 prior lines of systemic therapy

  • All patients had experienced failure of anti–PD-1 therapy

  • Patients treated with 350 mg evalstotug received more doses (mean, 7.2) compared with reported ipilimumab or tremelimumab dosing; no dose reductions occurred

  • Three patients have tolerated their first 1-gram evalstotug infusion; clearing the DLT observation period is anticipated by early June

    • Population PK modeling suggests that 1 g flat dose will enable over 98% of patients to maintain Cmin levels greater than EC50 throughout treatment potentially driving clinical benefit

• Evalstotug was generally well-tolerated with relatively low incidence and severity of immune-mediated AEs

  • Four patients experienced Grade 3 related treatment-emergent AEs

  • No Grade 4 or 5 related TEAEs were observed

  • Two patients experienced Grade 3 immune-related TEAEs (diarrhea [evalstotug 350 mg] and diabetic ketoacidosis [evalstotug 700 mg])

  • Only two treatment related discontinuations

• Evalstotug demonstrated clinical benefit in heavily pre-treated patients (data cut as of April 30, 2024)

  • Responses in three of eight patients who received evalstotug 350mg

    • One confirmed complete response in cervical carcinoma

    • One confirmed partial response in gastroesophageal carcinoma

    • One unconfirmed partial response in cutaneous melanoma patient who was dose escalated and who remains on therapy

  • Disease control rate of 52%

    • Three patients (two with cutaneous melanoma, one with metastatic small cell lung cancer) remained without progression for greater than 1 year (69 weeks)

    • One uveal melanoma patient without progression for 9.8 months

A copy of the presentation materials can be accessed on the "Publications" section of the Company's website at  once the presentation has concluded.

About Evalstotug (BA3071)

Evalstotug, is a CAB anti-CTLA-4 antibody that is being developed as an immuno-oncology agent with the goal of delivering efficacy at least comparable to the approved anti-CTLA-4 antibodies, but with lower toxicities due to the CAB's tumor microenvironment-restricted activity. This may enable safer anti-CTLA-4 antibody combination therapies, such as with anti-PD-1 antibody checkpoint inhibitors, and potentially broaden the patient population tolerant to combination therapy and deliver greater efficacy. Like our other CAB candidates, this Phase 2 clinical asset is designed to be conditionally and reversibly active in the tumor microenvironment. Evalstotug is being developed as a potential therapeutic for several solid tumor indications that are known to be responsive to CTLA-4 treatment in combination with a PD-1 blocking agent.