GRTS - Gritstone vaccine-based immunotherapies show promise versus solid tumors in trial

Gritstone bio ( NASDAQ: GRTS ) said its SLATE vaccines (version 1 and SLATE-KRAS) showed early evidence of efficacy with a 39% molecular response rate in evaluable patients with late-line microsatellite-stable colorectal cancer (MSS-CRC) and non-small cell lung cancer (NSCLC) in a phase 1/2 trial.

The company presented initial data with SLATE-KRAS, a shared mutant KRAS-specific neoantigen vaccine candidate, plus updated data using the first version of the vaccine (SLATE v1), which contains both KRAS and non-KRAS neoantigens at the the 2022 European Society for Medical Oncology (ESMO) Congress.

The phase 1/2 study is evaluating of both SLATE v1 (in 26 people) and SLATE-KRAS (in 12 people) in combination with Bristol Myers Squibb's Opdivo (nivolumab) and Yervoy (ipilimumab) in total 38 patients with metastatic solid tumors harboring select KRAS mutations. The majority of patients enrolled (31/38) had either advanced NSCLC (n=18) or MSS-CRC(n=13).

SLATE-KRAS and SLATE v1 showed a favorable safety and tolerability profile and also consistent and potent immunogenicity, the company said in a Sept. 12 press release.

Gritstone said 39% (7/18) molecular response rate in evaluable patients with MSS-CRC and NSCLC. In 18 patients with NSCLC, a molecular response was correlated with extended OS.

The company added that patients with NSCLC with a molecular response showed a median OS (9.6 months) than those without (4.5 months).

Gritstone noted that SLATE-KRAS vaccine candidate elicited robust KRAS neoantigen-specific CD8+ T cell responses.

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