A phase I study of CX-4945 administered orally twice daily to patients with advanced basal cell carcinoma.

Abstract

TPS10080 Background: Smoothened inhibitors (SMOi) targeting the Hedgehog (Hh) pathway have been approved for the treatment of patients with locally advanced Basal Cell Carcinoma (laBCC) or metastatic BCC (mBCC). Unfortunately, resistance against SMO inhibitors (SMOi) can develop. Targeting the signaling cascade downstream of SMO, in this case via a novel small molecule inhibitor, could obviate this issue. Casein Kinase 2 (CK2) affects the terminal component of the Hh signaling pathway by promoting Gli2 stability and Gli2’s interaction with target genes. Given the interplay between CK2 and GLI-2 and the importance of Hh signaling activation, CX-4945, a potent CK2 inhibitor, may provide benefits for the BCC patients with resistance or intolerance to SMOi. Methods: A phase I trial (NCT03897036) to explore various treatment durations of CX-4945 was designed for patients with laBCC or mBCC; with endpoints include safety (CTCAE v5) and objective response rate by RECIST 1.0 for mBCC and composite response for laBCC. Major eligibility criteria include progression or intolerability to SMO inhibitors; laBCC patients must not be surgical candidates and must have received prior radiation unless contraindicated, and basosquamous histology is excluded. The first phase of the trial uses a 3+3 design to test the tolerance of a CX-4945 dose of 1000 mg bid for a duration of 28 days continuously. If 2 out of 3, or 2 out of 6 patients experience a DLT, the regimen of 1000 mg bid for 21 days followed by 7 days off (already tested in prior CX-4945 Phase I trials in other tumor types) will be selected as the recommend phase 2 dose (RP2D). Upon determining the RP2D, a dose-expansion phase will further evaluateCX-4945 in two cohorts (laBCC & mBCC), with 10 patients enrolled in each. Currently, we are enrolling patients and collecting sufficient data for the determination of RP2D in this patient population; thus, further assessments are required to determine the safety, tolerability, and efficacy of CX-4945 in advanced BCC. Clinical trial information: NCT03897036.