Synthekine has reported positive initial data from a Phase Ia/Ib clinical trial of STK-012, a treatment for advanced solid tumours.

STK-012, an α/β biased IL-2 partial agonist, is designed to selectively stimulate CD25+ antigen-activated T cells.

The trial results, which included 47 subjects in the Phase Ia dose escalation portion, showed that STK-012 monotherapy was demonstrated to have a favourable efficacy, safety, pharmacokinetic, and pharmacodynamic profile.

Following the successful completion of the Phase Ia portion, the company initiated the Phase Ib study in September last year.

The Phase Ib study focuses on dose expansion cohorts to evaluate STK-012 as a single agent at the recommended Phase II dose in selected solid tumour types such as renal cell carcinoma (RCC) and non-small cell lung cancer (NSCLC).

In the trial, treatment-related adverse events (TRAEs) were mostly observed to be Grade 1 or 2 in severity and were reversible with standard management.

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Rash, fatigue, reactions at the injection site, nausea, and arthralgia were found to be the most common TRAEs reported.

Based on the observed pharmacokinetics, with a half-life of approximately four days, a schedule of once every three weeks was advanced beyond the 0.75mg dose at the time of the monotherapy dose escalation.

STK-012 showed selectivity for T cells expressing IL-2Rα (CD25), as evidenced by pSTAT5 induction.

The drug also demonstrated a dose-proportional increase in IFNγ and activated proliferating CD8 T cells while limiting the expansion of NK cells and Tregs.

Out of 40 subjects evaluated for efficacy, three achieved a partial response and 12 had stable disease as their best overall response.

Several subjects also exhibited durability of response.

Synthekine chief medical officer Naiyer Rizvi said: “We are excited to report multiple objective responses with STK-012 monotherapy, driven by robust induction of interferon‐gamma (IFNγ) and selective expansion of antigen-activated T cells.

“At the same time, we do not see the severe toxicities typically associated with IL-2 treatments, such as hypotension, capillary leak syndrome, or transaminitis. We look forward to completing the dose expansion portion of this study to further evaluate its potential for patients.”