This Phase 1/2 trial was designed to evaluate the safety profile and efficacy of orally administered ACP-196 in patients with relapsed or refractory CLL/SLL. ACP-196 is a second generation BTK inhibitor that is more selective than the first generation BTK inhibitor ibrutinib. Bruton’s tyrosine kinase (BTK) is an enzyme involved in B cell receptor pathway signaling that has been shown to be critical for CLL cell survival. Trials with ibrutinib established BTK as an effective therapeutic target for the treatment of CLL.
As part of the trial, patients were treated continuously with escalating doses of ACP-196, once or twice daily. No dose limiting toxicities were identified and 100 mg twice daily was established as the most efficacious dose. The median age of the patients and number of prior therapies were 62 years and 3 prior therapies respectively. The median time on the study was 10.3 months. As of June 2015 there were 60 patients who were evaluable for response.
The overall response rate was 93% for all patients and 100% in the deletion 17p patient. ACP-196 was well tolerated, with 93% of patients remaining on treatment. The most common adverse events were headache and diarrhea. No disease progression has occurred to date.
Results from this study show that ACP-196 is a highly potent and selective oral BTK inhibitor with a favorable safety profile. Currently there is a Phase 3 trial comparing ACP-196 to Ibrutinib in Patients with High Risk CLL open to eligible patients at Weill Cornell Medicine.