Botensilimab/Balstilimab Clinical Responses in Refractory Sarcomas Presented at ESMO 2024

Agenus Inc. (“Agenus”) (Nasdaq: AGEN), a leader in developing novel immunological agents to treat various cancers, presented data today at the European Society for Medical Oncology (ESMO) Congress held in Barcelona, Spain. The data from a Phase 1 study of botensilimab (BOT), an investigational Fc-enhanced CTLA-4 inhibitor, in combination with balstilimab (BAL), an investigational PD-1 antibody, showed clinical activity in patients with refractory sarcomas, a population with limited treatment options.

"The continued activity with additional patients and longer follow-up of BOT/BAL in this study reinforces it's potential as an important treatment option for patients with sarcomas," said Dr. Breelyn A Wilky, University of Colorado Cancer Center. "The deep and durable responses we are observing, particularly in late line patients with poorly immunogenic or ‘cold’ sarcomas like visceral angiosarcoma, leiomyosarcoma, and dedifferentiated liposarcoma, are significant. These findings highlight the potential of BOT/BAL to deliver extended survival and a meaningful clinical benefit for patients who previously had very limited options."

Study Highlights

• 64 patients with relapsed/refractory sarcomas (median of 3 prior lines of therapy) were treated with 1 or 2 mg/kg BOT + 3 mg/kg BAL.
• 52 patients were efficacy evaluable with at least one post-baseline 6-week imaging scan. ORR and DOR reporting will be based on the unconfirmed response in this cohort.
• Majority of sarcoma subtypes included angiosarcoma (39%) and leiomyosarcoma (34%).

Clinical Findings

• 23% overall response rate (ORR) was observed in the full sarcoma cohort, with a median duration of response (DOR) of 21.7 months. 12-month overall survival (OS) was 69% and the median OS was not reached.
• 39% ORR achieved in the angiosarcoma subtype (33% in cutaneous and 44% in visceral), with a median DOR of 21.7 months. 12-month OS was 64% and the median OS was not reached.
  • A representative patient with visceral angiosarcoma achieved a durable response, ongoing beyond 3 years, that has been maintained off-therapy.
• The adverse event profile of BOT+ BAL was manageable and reversible with no new safety signals identified.

"The updated sarcoma data presented at ESMO underscore the transformative potential of botensilimab and balstilimab for patients with refractory sarcomas who have exhausted other treatment options," said Dr. Steven O’Day, Chief Medical Officer at Agenus. "Seeing these metastatic sarcoma patients experience tumor reduction, with significant and durable responses is incredibly encouraging. BOT/BAL not only offers hope to patients with sarcoma but also holds promise for redefining the standard of care across other historically IO-resistant cancers."