Lyell Immunopharma Inc (NASDAQ:LYEL) shares are trading lower on Wednesday on a heavy session volume of 5.79 million shares as per data from Benzinga Pro.

The company released initial clinical and translational data from its Phase 1 trial of LYL797, its first-generation reprogrammed ROR1 CAR T‑cell product candidate enhanced with proprietary anti-exhaustion technology.

This initial dataset of 20 treated patients includes 16 patients with TNBC and four patients with non-small cell lung cancer and demonstrated dose-dependent antitumor clinical activity and the ability of LYL797 CAR T cells to proliferate, infiltrate tumors, and kill cancer cells in patients with relapsed/refractory disease.

Patients with TNBC treated with LYL797 had an objective response rate (ORR) of 40% and clinical benefit rate (CBR) of 60% at the 150 x 106 CAR T cell dose level, with a CBR of 38% across all dose levels evaluable to date.

Common treatment-related adverse events in patients without lung metastases included Grade 1 and 2 cytokine release syndrome (CRS) headache and the expected cytopenia from lymphodepletion.

No reports of immune effector cell-associated neurotoxicity syndrome (ICANS) attributed to LYL797.

Pneumonitis occurred in patients with lung metastases. The company said dose escalation continues separately and more gradually in those patients.

No dose-limiting toxicities have been reported in patients without lung involvement.

The company reported one death (Grade 5) due to respiratory failure on Day 41.

All patients are now receiving prophylactic steroids before LYL797 treatment.

Lyell says the adverse event of Grade > 3 pneumonitis occurred only in patients with TNBC and lung metastases, separating dose escalation into two cohorts based upon lung involvement (lung primary, lung metastatic disease, or pleural effusion).

Price Action: LYEL shares are down 35.9% at $1.31 at last check Wednesday.