Partial Response Achieved With Atezolizumab, Cobimetinib in Pretreated CRC

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In this research, investigators evaluated the efficacy of atezolizumab with cobimetinib for patients with heavily pretreated metastatic CRC.
In this research, investigators evaluated the efficacy of atezolizumab with cobimetinib for patients with heavily pretreated metastatic CRC.

Atezolizumab with cobimetinib may yield a partial response in some patients with heavily pre-treated metastatic colorectal cancer (CRC), according to research being presented at the 2018 Gastrointestinal Cancers Symposium in San Francisco, California.

Microsatellite stability (MSS), a common feature of CRC, is linked to a poor response to PD-1/PD-L1 inhibition. MEK inhibition with cobimetinib may, however, improve the response rate to checkpoint inhibition.

For this phase 1b study (ClinicalTrials.gov Identifier: NCT01988896), researchers evaluated the safety and efficacy of atezolizumab, a PD-L1 inhibitor, with cobimetinib for patients with heavily pretreated metastatic CRC.

Of 84 enrolled patients, 66 had received at least 5 prior therapies; 29 had MSS, 8 had low MS instability, and 1 had high MS instability.

The median follow-up was 14.3 months. Seven patients had a confirmed partial response: 3 with MSS, 3 with unknown MSS status, and 1 with low MS instability. The median duration of response was 14.8 months.

Less than one-third (31%) of patients had a partial response or stable disease. The median progression-free survival was 1.9 months; median overall survival was 10 months.

Treatment-related grade 3 to 4 adverse events were noted in 37% of patients.

The authors concluded that the combination “demonstrated a tolerable safety profile and improvements in [overall survival] vs those reported with [standard of care] in heavily pretreated [patients] with [metastatic] CRC.”

Reference

Bendell JC, Bang YJ, Chee CE, et al. A phase Ib study of safety and clinical activity of atezolizumab (A) and cobimetinib (C) in patients (pts) with metastatic colorectal cancer (mCRC). Oral presentation at: 2018 Gastrointestinal Cancers Symposium; January 18-20, 2018; San Francisco, CA.

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