The aim was defining the recommended phase 2 dose (RP2D) using a 3 + 3 dose-escalation design. Second, pharmacokinetics and pharmacodynamics were explored.
Twenty-four patients with KRASm PDAC, NSCLC or CRC were treated with RMC-4630 weekly on days 1-2 and LY3214996 daily in 28-day cycles; nineteen were evaluable for dose-limiting toxicities (DLT). DLTs were reported at three of the four explored dose levels, preventing further escalation. Three DLTs were due to grade 3 thrombocytopenia. The other three resulted from grade 2 decreased left ventricular ejection fraction, and grade 3 acute kidney injury and diarrhea. At dose level 1b (100 mg RMC-4630; 200 mg LY3214996), no DLTs were reported. Pharmacokinetic analysis revealed high interpatient variability and intrapatient correlation with exposure to both agents. An exposuretoxicity relationship was not established. Pharmacodynamic analysis showed a significant decrease in phosphorylated S6-ribosomal protein (p = 0.034), however radiological responses were not observed.
Sufficient exposure to RMC-4630 and LY3214996 was not reached due to the toxicity profile of the combination. Tumor response was not demonstrated at the explored dose levels. Therefore, the dose escalation was discontinued, and the RP2D was not determined.
PDAC has high mortality rates and limited treatment options. KRAS mutations are present in > 90% of patients with PDAC, causing constitutive activation of the MAPK pathway. Preclinical studies demonstrated synergistic antitumor activity in in vivo and in vitro KRAS-mutant PDAC models by combining SHP2 and ERK inhibition. Therefore, the safety of combining SHP2 inhibitor RMC-4630 and ERK inhibitor LY3214996 was evaluated in this phase I trial.
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