STCube Reports Early Results from Phase 2a Trial in Extensive-Stage Small Cell Lung Cancer: 2 PR and 1 SD out of 3 Patients

STCube has revealed the initial clinical results of the anti-BTN1A1 immune checkpoint inhibitor Nelmastobart in small cell lung cancer for the first time.

STCube announced on the 18th that in the Phase 2a clinical trial for recurrent or refractory extensive-stage small cell lung cancer (ES-SCLC), among the three patients who underwent tumor evaluation, two achieved partial response (PR) and one had stable disease (SD), demonstrating high anticancer efficacy.

These patients were terminal cancer patients who relapsed after previous treatments including immune checkpoint inhibitor combination therapy and cytotoxic chemotherapy, with an average survival period of only 2 to 3 months remaining. Currently, STCube is conducting Phase 1b/2 clinical trials approved by the U.S. Food and Drug Administration (FDA) and domestic authorities to evaluate the safety and efficacy of Nelmastobart combined with paclitaxel in patients with second-line or later treatment for extensive-stage small cell lung cancer.

In a Phase 1 clinical trial evaluating the safety of Nelmastobart monotherapy in patients with advanced solid tumors, two out of three small cell lung cancer patients showed stable disease (SD). Furthermore, through immunohistochemistry (IHC) analysis, it was confirmed that the BTN1A1 expression rate was high in SD patients and low in patients with progressive disease (PD), revealing the efficacy of BTN1A1-targeted immuno-oncology treatment. The SD patient from the Phase 1 trial who is still alive has maintained a treatment response for over 24 months.

Extensive-stage small cell lung cancer refers to the stage where metastasis has spread beyond the lungs to other organs. Due to its high malignancy and rapid metastasis, about 70% of small cell lung cancer cases are classified as extensive-stage at diagnosis. Surgery is often not an option, so chemotherapy is the standard treatment, but the effectiveness significantly decreases in second- and third-line treatments after relapse.

In the Phase 1b small cell lung cancer trial (6 patients), safety and tolerability were confirmed in both the low-dose group (Nelmastobart 400mg, paclitaxel 175mg/m2) and the high-dose group (Nelmastobart 800mg, paclitaxel 175mg/m2). Dose-limiting toxicity (DLT) and maximum tolerated dose (MTD) were not observed at any dose level.

In the ongoing Phase 2a trial, the recommended dose for Phase 2b will be determined among two dose cohorts involving 56 patients. Subsequently, an additional 62 patients will be recruited for the Phase 2b trial to conduct a comparative study with a control group.

An STCube representative introduced, "This is the time when the value of Nelmastobart as a true first-in-class innovative drug is finally being validated through clinical results." They added, "For anticancer drugs, not only efficacy but also the absence of toxicity and good tolerability are essential to improve patients' quality of life. In that regard, Nelmastobart is proving an excellent safety and efficacy profile."