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ESMO Asia 2020: Novel PD-L1 Antibody Shows Activity in Advanced MSI-H/dMMR Tumors


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Envafolimab (also known as KN035), a novel PD-L1 antibody, demonstrated antitumor activity and was safe in patients with diverse, advanced microsatellite instability–high/mismatch repair–deficient (MSI-H/dMMR) tumors, according to findings presented by Shen et al at the ESMO Asia Virtual Congress 2020 (Abstract 70M0).

Researchers explained that envafolimab is a novel anti–PD-L1 single-domain antibody formulated for subcutaneous injection. The team evaluated the efficacy and safety of envafolimab in patients with advanced tumors in a single-arm, phase II study.

Study Details

The study enrolled 103 adult patients with previously treated MSI-H/dMMR advanced cancer in China, including 65 patients with colorectal cancer,18 with gastric cancer, and 20 patients with other tumor types. Eligible patients had failed one or more lines of systemic treatment; specifically, 41 of 65 patients with colorectal cancer failed two or more lines of prior therapies including a fluoropyrimidine, oxaliplatin, or irinotecan.

All patients were treated with envafolimab at 150 mg administered subcutaneously weekly until disease progression, unacceptable toxicity, or withdrawal.

The primary endpoint was the objective response rate per Response Evaluation Criteria in Solid Tumors version 1.1 by blinded independent radiology review.

Results

Regarding the primary endpoint, with median follow-up of 11.5 months, patients in the overall population demonstrated a confirmed objective response rate of 42.7% (95% confidence interval [CI] = 33.0%–52.8%).

The objective response rate was 43.1% (95% CI = 30.8%–56.0%) in individuals with colorectal cancer; among the patients with colorectal cancer, the 24 for whom one prior line of treatment had failed showed a 62.5% objective response rate (95% CI = 40.6%–81.2%) and the 41 patients for whom two or more prior lines had failed demonstrated an objective response rate of 31.7% (95% CI = 18.1%­48.1%). The 18 patients with gastric cancer showed an objective response rate of 44.4% (95% CI = 21.5%­–69.2%), and the objective response rate was 40.0% (95% CI = 19.1%–63.9%) in patients with other tumors.

The median progression-free survival per blinded independent radiology review was 11.1 months in the overall population, 7.2 months in the colorectal cancer population, and not reached for patients in the gastric cancer or other tumors population.

Median overall survival and the median duration of response were not reached in any population. The 12-month overall survival rate was 74.6% in the overall population and the colorectal cancer, gastric cancer, and other tumors cohorts demonstrated 12-month overall survival of 72.9%, 83.3%, and 75.0%, respectively.

Similar results were found according to investigator assessment: the overall population had an objective response rate of 41.7%. Among patients with colorectal cancer, those who had failed one prior treatment had an objective response rate of 58.3%, and those who had failed two or more prior lines had an objective response rate of 29.3%. Patients with gastric cancer demonstrated a 50% objective response rate, and those with other tumors had a 40.0% objective response rate.

All-grade treatment-related adverse events occurred in 84.5% of the overall population, and 15.5% of patients had grade 3 or 4 treatment-related adverse events. No grade 5 treatment-related adverse event occurred.

The most common immune-related adverse events were hypothyroidism (15.5%) and hyperthyroidism (11.7%). No pneumonitis or colitis were reported. Local injection site reactions (grades 1–2) occurred in 8.7% of patients.

Based on presented findings, the investigators concluded that envafolimab demonstrated antitumor activity with a manageable safety profile in heavily pretreated patients with dMMR/MSI-H advanced cancers.

Disclosure: For full disclosures of the study authors, visit oncologypro.esmo.org.

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.
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