Abstract 1453P
Background
High levels of transforming growth factor (TGF)-β in the tumor microenvironment (TME) represents a primary mechanism for induction of epithelial-to-mesenchymal transition, immune evasion and cancer stem-like cells (CSC) formation. Previous studies demonstrated that vactosertib, a potent, highly selective, oral TGF-β inhibitor, can augment the cytotoxic effect of paclitaxel by suppressing CSC formation. Here, we report the phase I results of vactosertib in combination with paclitaxel as a second-line treatment in metastatic gastric adenocarcinoma (mGC).
Methods
Eligible patients (pts) are ≥19 years old, have ECOG status ≤1, and have progressed on the first line treatment of mGC. The primary objective is to assess the safety and recommended phase II dose (RP2D) of vactosertib (100, 200, and 300 mg BID) given 5 days on/2 days off and weekly paclitaxel (80 mg/m2) along with evaluation of the anti-tumor activity.
Results
12 pts were enrolled in the phase I study (6, 3, and 3 pts in 100, 200, and 300 mg BID, respectively). Median age was 49 (range, 39-65), 50% were male, and 75% had a gastrectomy. At all cohorts, no dose limiting toxicity and cardiac toxicity were observed. The most frequently reported treatment-related adverse events (TRAEs) were anemia (58%), anorexia (42%), fatigue (33%) and dyspepsia (33%). One case of grade 3 anorexia was reported as treatment-related serious AE. In 200 and 300 mg BID cohorts, median PFS was estimated to be 5.5 months. ORR and DCR at 12 weeks were 16.7% and 83.3%, respectively. One patient showed complete response of target lesion with overall RECIST evaluation of partial response. Two patients are ongoing cycle 7 and cycle 11 treatment as of May 2020. Pharmacokinetic analysis indicated that the half-life of vactosertib was approximately 3 hours, supporting BID dosing regimen. The changes in the level of biomarkers for TGF-β signaling pathway, including pSMAD and circulating cytokines, were attenuated after vactosertib treatment.
Conclusions
The combination of vactosertib and paclitaxel had an acceptable tolerability and safety profile. Phase II study of the combination of vactosertib 300mg BID and weekly paclitaxel is now underway.
Clinical trial identification
NCT03698825.
Editorial acknowledgement
Legal entity responsible for the study
MedPacto, Inc.
Funding
MedPacto, Inc.
Disclosure
C-Y. Ock: Leadership role, Shareholder/Stockholder/Stock options, Full/Part-time employment: Lunit; Advisory/Consultancy, Shareholder/Stockholder/Stock options: Medpacto; Advisory/Consultancy: Y-Biologics. J.B. Bae, J.K. Lee, D.W. Kang, K.B. Hahm: Shareholder/Stockholder/Stock options: Medpacto. S. Hwang: Leadership role, Shareholder/Stockholder/Stock options, Full/Part-time employment: Medpacto. S-J. Kim: Advisory/Consultancy, Leadership role, Shareholder/Stockholder/Stock options: Medpacto, Inc; Advisory/Consultancy, Leadership role, Shareholder/Stockholder/Stock options: Theragen Etex Co. All other authors have declared no conflicts of interest.