Rezatapopt Shows Promise in Restoring Function to Mutant p53 in Early Clinical Trials
A fresh study published in Nature Medicine demonstrates that the small molecule rezatapopt can bind to and restore tumor suppressor function in cells with the Y220C mutation of the p53 gene. Phase 1 clinical trial data provides initial proof of concept for this therapeutic approach.
Understanding p53 and the Y220C Mutation
The p53 gene is a critical tumor suppressor, often referred to as the “guardian of the genome.” It plays a vital role in preventing cancer by regulating cell division, repairing DNA, and initiating programmed cell death (apoptosis) when cells develop into damaged. Mutations in the TP53 gene are found in approximately 50% of all human cancers.
The Y220C mutation is a specific alteration in the p53 gene that creates a cavity in the protein structure. This mutation occurs in an estimated 125,000 new cancer cases each year. It leads to a loss of normal p53 function, contributing to cancer development. Researchers have been working to develop “reactivators” – molecules that can restore function to this mutated protein.
How Rezatapopt Works
Rezatapopt (PC14586) is an investigational oral drug designed to selectively bind to p53 proteins with the Y220C mutation. By binding to the mutated protein, rezatapopt stabilizes the p53 protein in its wild-type conformation and restores its ability to function as a tumor suppressor. Recent research has shown that rezatapopt likewise binds to and stabilizes p53 with Y220N and Y220S mutations, though with varying degrees of effectiveness.
Structural studies, including X-ray crystallography, have revealed a conserved binding mode of rezatapopt to all three mutant forms of p53 (Y220C, Y220N, and Y220S), highlighting key interactions between the drug and the protein.
Phase 1 Clinical Trial Results
A Phase 1 clinical trial evaluated the safety and efficacy of rezatapopt in 77 patients with advanced solid tumors harboring a TP53 Y220C mutation. The maximum tolerated dose was determined to be 1500 mg twice daily. A recommended Phase 2 dose of 2000 mg once daily with food was selected based on safety, efficacy, and pharmacokinetic data.
Key findings from the trial include:
- 99% of patients experienced at least one adverse event.
- 38% of patients experienced a grade 1 or 2 adverse event.
- The most common adverse events were nausea (58%), vomiting (44%), increased blood creatinine (39%), fatigue (39%), and anemia (36%).
- Treatment-related adverse events led to discontinuation of rezatapopt in 3% of patients.
Future Directions
The data from this Phase 1 study are encouraging and support further investigation of rezatapopt as a potential therapy for cancers driven by p53 Y220C mutations. Researchers are continuing to explore the potential of developing pan-Y220C/N/S reactivators to benefit a broader range of patients. Further clinical trials will be necessary to confirm these findings and determine the long-term efficacy and safety of rezatapopt.
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