BeiGene presents Phase 1 tislelizumab data at AACR

BeiGene announced the presentation of long-term Phase 1 data and results of structural and binding mechanistic analyses on its investigational anti-PD1 inhibitor, tislelizumab, in posters at the American Association for Cancer Research, or AACR. The multi-center, open-label Phase 1 trial of tislelizumab as monotherapy in advanced solid tumors is being conducted in Australia, New Zealand, the United States, Taiwan, and South Korea and consists of dose escalation, schedule expansion, fixed dose expansion and indication expansion. This first-in-human, or FIH, trial is fully enrolled with over 450 patients. As of October 27, 2018, 65 patients received tislelizumab for more than 12 months and were included in this long-term exposure, or LTE, analysis. These 65 patients were from both the dose-escalation and dose-expansion phases. Most patients with LTE received tislelizumab at 5 mg/kg Q3W, while additional patients received 2 mg/kg Q3W, 2 mg/kg Q2W, 5 mg/kg Q2W and 200 mg Q3W. The most common tumor types were non-small cell lung cancer, hepatocellular cancer and bladder and ovarian cancers. With a median follow-up of 27.2 months, the objective response rate, or ORR, among patients with LTE was 68%. Four patients achieved complete response, including patients with cutaneous squamous cell carcinoma, endometrial, bladder and esophageal cancers. All four patients were PD-L1 positive. Partial responses and stable disease were observed in both PD-L1 positive and PD-L1 negative tumors. The median duration of response was 21.1 months in those with LTE. LTE to tislelizumab was generally well-tolerated when given for more than 12 months. As of the data cutoff, 52 of 65 patients experienced one or more treatment-related adverse event, or TRAE, most of which were mild to moderate in severity. Rash was the only TRAE reported in more than 15% of patients, and no rash event of grade 3 or higher occurred. Serious TRAEs occurred in three patients, including pyrexia and arthritis and all resolved. Three patients experienced AEs that eventually led to discontinuation. There were no fatal AEs.

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