Agenus Presents Clinical Data Demonstrating Durable Responses of Botensilimab/Balstilimab Combination in Metastatic Microsatellite Stable Colorectal Cancer at ASCO GI

Global, randomized Phase 2 trials of botensilimab/balstilimab in MSS CRC and other indications have commenced; plan to initiate Phase 3 CRC trial in 2023

Agenus (Nasdaq: AGEN), an immuno-oncology company with a pipeline of immunological agents targeting cancer and infectious disease, today announced clinical data from the MSS CRC (microsatellite stable colorectal cancer) 70 patient cohort of a Phase 1b study of botensilimab (multifunctional Fc-enhanced anti-CTLA-4) in combination with balstilimab (anti-PD-1) in patients with chemotherapy and/or immunotherapy-resistant tumors. The larger dataset continues to demonstrate that this combination offers superior efficacy and durability compared to what has been reported for standard of care and other investigational therapies in third line metastatic MSS CRC. The data were presented in the opening late-breaking oral session at the American Society of Clinical Oncology – Gastrointestinal Cancers Symposium (ASCO GI) in San Francisco, CA on Saturday Jan 21 2023.

“This data highlight the deep and durable responses achieved with botensilimab and balstilimab in advanced MSS CRC, underscoring remarkable benefit for these patients who have failed standard of care or other investigative therapies. With over 300 patients enrolled to date, botensilimab alone and in combination with balstilimab have demonstrated durable clinical responses across nine cold and treatment-resistant cancers,” said Steven O’Day, MD, Chief Medical Officer at Agenus. “Our top priority is to advance this combination in global randomized trials with the intent to bring this important treatment to patients expeditiously.”

“MSS CRC accounts for over 95% of metastatic CRC cases and is characterized by tremendous unmet need, as available treatments have reported single digit responses rates,” said Anthony El-Khoueiry, MD, Phase I Program Director and Associate Director for Clinical Research at the USC Norris Comprehensive Cancer Center, Keck Medicine of USC, and the Principal Investigator for the study. “The 23% response rate demonstrated by botensilimab plus balstilimab in this study supports rapid development of this combination in MSS CRC.”

Study Design and Highlights:

A total of 70 evaluable patients with refractory metastatic MSS CRC received either 1 or 2 mg/kg botensilimab every 6 weeks and 3 mg/kg balstilimab every 2 weeks.

Patient Demographics:

  • Heavily pre-treated, with a median of 4 prior lines of therapy
  • 31% had received prior immunotherapy

Objective responses:

  • 23% overall response rate
    • Other PD-(L)1 + CTLA-4 combinations in comparable patient populations have reported 1-5% response rates1,2
  • 69% of objective responses were ongoing at data cut-off
  • 76% disease control rate (complete response + partial response + stable disease)


  • 12-month overall survival of 63%
    • Reported 12-month overall survival for standard of care is ~25%
  • Median overall survival has not been reached


  • Manageable gastrointestinal toxicity with a differentiated overall safety profile

Presentation Details:

Abstract Title: Results from a phase 1a/1b study of botensilimab (BOT), a novel innate/adaptive immune activator, plus balstilimab (BAL; anti-PD-1 antibody) in metastatic heavily pretreated microsatellite stable colorectal cancer (MSS CRC) (NCT03860272)

Abstract Number: LBA8

Presenting Author: Anthony El-Khoueiry, MD, Phase I Program Director at the USC Norris Comprehensive Cancer Center, Keck Medicine of USC

Following the symposium, an archived version of the presentation will be available in the Publications section of the Agenus website at www.agenusbio.com.


1 Chen et al. JAMA Oncol. 2020

2 Overman et al. ASCO 2016

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