Turnstone Biologics Corp. ( TSBX ) stock is trading lower after the company released initial data from its Phase 1 STARLING trial of TIDAL-01 in metastatic microsatellite-stable colorectal cancer (MSS mCRC) on Thursday.

TIDAL-01 is a tumor-infiltrating lymphocyte therapy. In cancer therapy, tumor-infiltrating lymphocytes are removed from a patient’s tumor, grown in large numbers in a laboratory, and then given back to the patient to help the immune system kill the cancer cells.

As of the cutoff date of July 15, 2024, key takeaways from the initial data include the following:

Clinical Responses: Among the four evaluable MSS mCRC patients included in the study, Turnstone observed a 25% overall response rate (ORR) and a 50% disease control rate (DCR).

One patient demonstrated a deep and durable ongoing complete response (CR).

Durability of Response: 50% of patients showed sustained clinical benefit, with notable progression-free survival of over one year in the patient with ongoing complete response and six months for a patient with stable disease.

Translational Profile: The TIDAL-01 process demonstrated the ability to generate high-titer, polyclonal and multi-epitope tumor neoantigen-reactive T cells that expanded in the patient, persisted in the blood and correlated with an increase in CD8 T cell tumor infiltration.

Tolerability Profile: TIDAL-01 was generally well-tolerated and safety events observed were consistent with known AEs associated with the lymphodepletion regimen, and IL-2 and pembrolizumab administration.

In a second-quarter earnings release, Turnstone said its clinical development strategy for TIDAL-01 is now focused on “three high unmet medical need indications, including colorectal cancer, head and neck cancer, and uveal melanoma.”

The trial is currently enrolling patients with colorectal cancer, head and neck squamous cell carcinoma, and uveal melanoma. The company has deprioritized cutaneous melanoma and breast cancer.

As of June 30, 2024, cash, cash equivalents and short-term investments were $62.4 million. The company expects the combined cash, cash equivalents and short-term investments will be sufficient to fund its operations into the third quarter of 2025.

TSBX Price Action: Turnstone Biologics ( TSBX ) stock is down 57.53% at 93 cents at publication Thursday.

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