In a pivotal phase 2 trial, ponatinib, a third-generation tyrosine kinase inhibitor (TKI), was evaluated for its efficacy and safety in treating chronic-phase chronic myeloid leukemia (CP-CML) patients resistant to multiple prior TKIs. The study, known as PACE (Ponatinib Ph+ ALL and CML Evaluation), revealed that while ponatinib induced deep and durable responses, it also led to notable adverse events, particularly arterial occlusive events (AOEs), which were found to be dose-dependent.
The OPTIC (Optimizing Ponatinib Treatment in CP-CML) trial further explored this by assessing the benefit/risk ratio across three ponatinib starting doses: 45 mg, 30 mg, and 15 mg once daily. Patients were randomly assigned to these cohorts, with those in the 45 mg and 30 mg groups having their doses reduced to 15 mg upon achieving a response (BCR-ABL1IS transcript levels ≤1%). The primary endpoint was the response rate at 12 months.
Results showed that the 45 mg cohort achieved a 44.1% response rate, compared to 29.0% and 23.1% in the 30 mg and 15 mg cohorts, respectively. The study concluded that all three starting doses provided clinical benefit, but the 45 mg starting dose, reduced to 15 mg upon response, offered the best balance between efficacy and safety. This strategy not only maximized response rates but also minimized toxicity, particularly AOEs, which were significantly lower in the reduced-dose groups.
This trial underscores the importance of a tailored approach to TKI therapy in CP-CML, especially for patients resistant to prior treatments. The findings suggest that starting with a higher dose of ponatinib and reducing it upon achieving a response could be an effective strategy to manage CP-CML, offering hope for improved outcomes in this challenging patient population.
