The first important progress in targeting p53 mutations happened in the 1980s and 1990s when researchers found that aminoglycoside antibiotics could fix stop-codon mutations.
The development of targeted cancer therapies has progressed through several key milestones:
- 1985: Aminoglycosides were first identified as agents capable of correcting certain nonsense (amber) mutations, thereby restoring the function of mutated p53.
- Early 2000s (PRIMA-1 / APR-246): PRIMA-1, later known as eprenetapopt (APR-246), was among the first small molecules demonstrated to restore normal p53 function and induce apoptosis in tumor cells harboring p53 mutations.
- 2004 (MDM2 Inhibitors): MDM2 inhibitors, like Nutlins, were created to stop MDM2 from breaking down p53, helping it to protect against tumors again.
Although p53 was long thought impossible to target with drugs, new treatments aimed at specific p53 sites, including the difficult Y220C mutation, have recently started clinical trials.
This section highlights the drug with potential to target p53 mutations as discussed at ASCO Breakthrough 2026.
At the 2026 ASCO meeting, Rezatapopt (formerly PC14586) was highlighted for its specificity in targeting p53 mutations.
Rezatapopt is an experimental targeted treatment designed for tumors with the TP53 Y220C mutation. Early trial results focused on patients with advanced solid tumors, especially ovarian cancer, who had many previous treatments. Rezatapopt (PC14586) is made to activate p53 in these tumors. This mutation weakens p53 function, but Rezatapopt attaches to the mutated protein, changes its shape, and restores its ability to fight tumors.
Clinical trials, including the PYNNACLE study, have demonstrated that Rezatapopt is effective against multiple cancers driven by the TP53 Y220C mutation, with the most pronounced effects observed in: Ovarian cancer, breast cancer (including triple-negative breast cancer), and lung cancer
Considerations for Selecting Treatment Options
Has genomic or biomarker testing confirmed the presence of the TP53 Y220C mutation?
Rezatapopt directly reactivates p53 in cancer cells. Taken by mouth, it attaches to a special spot created by the p53 Y220C mutation and helps the protein return to its normal working shape.
How Rezatapopt works after fixing p53’s shape includes:
1) DNA Binding: The p53 protein regains its capacity to bind directly to cellular DNA.
2) Gene Activation: Fixed p53 boosts the activity of certain genes, like CDKN1A and MDM2, to slow tumor growth. 3) Cell Death: It stops cancer cells from multiplying and causes them to die.
Looking Forward: Is Future p53 Therapeutic Strategies Based on RNAS?
Rezatapopt does not directly target or use RNA. But RNA is important in research for assessing and confirming how well the drug fights cancer.
Gene Expression: Researchers use RNA sequencing (RNA-seq) to assess the effects of Rezatapopt on gene expression.
Target Verification: Measuring changes in RNA levels helps researchers confirm that Rezatapopt works.
Long non-coding RNAs (lncRNAs) and antisense oligonucleotides (ASOs) act as natural or man-made controllers of the p53 tumor suppressor pathway. Together, they offer treatment methods to keep p53 stable, block its negative controllers, or turn it back on after DNA damage.
How lncRNAs Help Activate p53
Specific lncRNAs interact with the p53 pathway to enhance its tumor suppressor functions or maintain p53 protein stability.
Protein Stabilization: LncRNAs like PSTAR and DINO attach to RNA-binding proteins, including hnRNP K, helping them connect with and stabilize p53.
Decoys and Scaffolds: Some lncRNAs work like molecular decoys, trapping negative controllers like MDM2 away from p53 and stopping it from being broken down.
Transcriptional Amplification: Some lncRNAs are made when p53 is activated and connect with gene enhancer areas, helping to stop cell division and cause cell death.
How ASOs Help Activate p53 ASOs are man-made, single-stranded molecules designed to attach to and break down specific RNA targets. They are useful tools to block negative controllers of the p53 pathway:
Depleting Inhibitory lncRNAs: Many cancers produce too much of inhibitory lncRNAs, like PURPL or RMRP, which lower p53 activity. ASOs can bind to and degrade these lncRNAs, restoring p53 function. Blocking MDM2 and MDMX: MDM2 is the main blocker of p53 in cells. ASOs can target and destroy MDM2 mRNA, stopping it from blocking p53.
Finally, the Therapeutic Potential
In patients with normal p53 that is not working properly, lncRNA-based treatments or ASOs targeting MDM2 can quickly stop cancer cells from dividing or cause them to die.