8-K: Prelude Therapeutics Announces Promising Early Data for SMARCA2 Degrader PRT3789 in Phase 1 Trial

Prelude Therapeutics reports encouraging initial clinical activity and a tolerable safety profile for its SMARCA2 degrader, PRT3789, in a Phase 1 trial, showing objective responses in some patients with SMARCA4-mutated cancers.

Summary

• Prelude Therapeutics has released interim data from its Phase 1 trial of PRT3789, a novel SMARCA2 degrader.
• The trial included 65 patients, with 46 evaluable for efficacy, all with advanced solid tumors harboring SMARCA4 mutations.
• PRT3789 demonstrated tumor shrinkage in 7 out of 26 evaluable patients with non-small cell lung cancer (NSCLC) or esophageal cancer.
• Three patients achieved RECIST confirmed partial responses, two with esophageal cancer and one with NSCLC.
• The drug was generally well-tolerated, with no dose-limiting toxicities or study drug-related serious adverse events reported.
• The most common adverse events were mild to moderate, including nausea, decreased appetite, and fatigue.
• Pharmacokinetic data showed increased drug exposure with higher doses, and pharmacodynamic data indicated prolonged SMARCA2 degradation.
• The company plans to confirm the biologically active dose for PRT3789 by the end of the year and continue combination studies with docetaxel.
• A Phase 2 trial combining PRT3789 with pembrolizumab is expected to start in the second half of 2024.
• The data was presented at the European Society of Medical Oncology (ESMO) Congress 2024 and selected for a plenary session at the EORTC-NCI-AACR Symposium.

Sentiment

Score: 8

Explanation: The document presents positive initial clinical data with a good safety profile, suggesting a promising future for the drug. The company is also actively pursuing combination therapies and has a clear plan for further development. However, it is still early in the clinical trial process, and there are inherent risks associated with drug development.

Positives

• PRT3789 demonstrated anti-tumor activity in heavily pre-treated patients with limited treatment options.
• The drug showed a favorable safety profile with no serious drug-related adverse events.
• The observed pharmacodynamic effect was more prolonged than the pharmacokinetic half-life, indicating sustained target engagement.
• The study showed a positive correlation between tumor shrinkage and sustained SMARCA2 degradation.
• The company is actively pursuing combination therapies to enhance the efficacy of PRT3789.
• The data was selected for presentation at major medical conferences, highlighting its significance.

Negatives

• The study is still in Phase 1, and the results are preliminary.
• The number of patients with confirmed partial responses is relatively small.
• The majority of patients experienced some adverse events, although they were mostly mild to moderate.
• No tumor shrinkage was observed in the 20 patients with tumor types other than NSCLC and esophageal cancer.

Risks

• The clinical trial is ongoing, and further data is needed to confirm the efficacy and safety of PRT3789.
• The company needs to successfully identify the biologically active dose and move into Phase 2 trials.
• There is a risk that the combination therapies may not be as effective as hoped.
• The development of new cancer therapies is inherently uncertain, and there is no guarantee of regulatory approval.
• The company is reliant on the success of its clinical trials and may face challenges in funding future development activities.

Future Outlook

The company expects to confirm the biologically active dose of PRT3789 by the end of 2024 and plans to initiate a Phase 2 trial combining PRT3789 with pembrolizumab in the second half of 2024. They also plan to continue monotherapy and docetaxel combination studies.

Management Comments

• Robin Guo, M.D., stated that the observation of durable stable disease and tumor regressions in Phase I monotherapy dose escalation, coupled with a tolerable emerging safety profile, is encouraging.
• Jane Huang, M.D., stated that the data represent initial proof of concept that selective SMARCA2 degradation can yield antitumor activity in certain SMARCA4 mutated cancers.
• Jane Huang, M.D., also mentioned the intention to confirm the biologically active dose for PRT3789 as monotherapy by year-end and continue to advance monotherapy and docetaxel combination studies.

Industry Context

This announcement is significant in the field of precision oncology, as it provides early clinical evidence for a novel approach to treating cancers with SMARCA4 mutations, which are known to be aggressive and have poor prognoses with current standard of care. The development of a selective SMARCA2 degrader addresses a high unmet medical need.

Comparison to Industry Standards

• The median progression-free survival for first-line SMARCA4-mutated NSCLC treated with chemoimmunotherapy is 2.7 months, with response rates around 22%.
• The observed partial responses and stable disease in the PRT3789 trial, in a heavily pre-treated population, suggest a potential improvement over current standards.
• Other companies are also exploring SMARCA2 inhibition, but Prelude's approach with a degrader is unique and may offer advantages in terms of potency and selectivity.
• Foghorn Therapeutics and Lilly have also been working on SMARCA2 inhibitors, but their approaches have faced challenges with selectivity.
• The development of a highly selective SMARCA2 degrader is a significant advancement, as previous attempts with inhibitors have struggled with selectivity.

Stakeholder Impact

• Shareholders may view the positive clinical data as a positive sign for the company's future prospects.
• Patients with SMARCA4-mutated cancers may benefit from a new treatment option.
• Employees may be motivated by the progress of the clinical trial.
• The company's partners may be encouraged by the positive results.

Next Steps

• Confirm the biologically active dose of PRT3789 as monotherapy by year-end 2024.
• Continue enrollment in backfill cohorts enriched for NSCLC and esophageal cancer patients with Class 1 mutations.
• Advance monotherapy and docetaxel combination studies in parallel.
• Initiate a Phase 2 trial combining PRT3789 with pembrolizumab in the second half of 2024.
• Present additional data at the EORTC-NCI-AACR Symposium on October 24, 2024.
• Continue development of the oral SMARCA2 degrader, PRT7732.
• Advance the first SMARCA2/4 Precision ADC in partnership with AbCellera.

Key Dates

Keywords

SMARCA2 degrader, PRT3789, SMARCA4 mutation, Non-small cell lung cancer, Esophageal cancer, Phase 1 trial, Precision oncology, Targeted therapy, Tumor shrinkage, Partial response, Clinical trial, Cancer treatment