Safety, pharmacokinetics and efficacy of HA121-28 in patients with advanced solid tumors and RET fusion-positive non-small-cell lung cancer: a multicenter, open-label, single-arm phase 1/2 trial

HA121-28, a promising multikinase inhibitor, mainly targets rearranged during transfection (RET) fusions and selectively targets vascular endothelial growth factor receptor-2, endothelial growth factor receptor, and fibroblast growth factor receptor 1-3. The safety, pharmacokinetics, and efficacy of HA121-28 were assessed in advanced solid tumors (phase 1, ClinicalTrials.gov NCT03994484) and advanced RET fusion-positive non-small-cell lung cancer (RET-TKI naive NSCLC, phase 2, ClinicalTrials.gov NCT05117658). HA121-28 was administered orally in doses range from 25 to 800 mg under the 21-day on/7-day off scheme for a 28-day cycle in phase 1 trial. The recommended dose identified in phase 1 (450 mg) was administered for patients during phase 2. The primary endpoints were the maximum tolerated dose (MTD) in phase 1 and the objective response rate (ORR) in phase 2. 162 patients were enrolled in phase 1 and 48 in phase 2. A total of 600 mg once daily was set as MTD. Across 100–800 mg, the exposure of HA121-28 increased in a dose-dependent manner. Consistent between both trials, diarrhea, rash, and prolonged QTc interval, were the most reported treatment-emergent adverse events. 40.0% (phase 1) and 62.5% (phase 2) patients experienced grade ≥3 treatment-related adverse events, respectively. The overall ORR was 26.8% and the median progression-free survival (PFS) was 5.5 months among 97 NSCLC patients with advanced RET fusion receiving a dose at ≥450 mg once daily. HA121-28 showed encouraging efficacy in advanced RET fusion NSCLC and its toxicity was tolerable in most patients. Nevertheless, cardiotoxicity is a notable concern that warrants careful attention.