Casdatifan, an oral HIF-2α inhibitor, has shown promising clinical activity in patients with metastatic clear cell renal cell carcinoma (ccRCC) who have progressed on prior therapies. Data from the phase 1/1b ARC-20 study, presented at the 2024 EORTC-NCI-AACR Symposium, revealed durable responses and disease control with acceptable tolerability.
The dose-escalation phase of the ARC-20 study evaluated casdatifan at doses ranging from 20 mg to 200 mg daily. No dose-limiting toxicities (DLTs) were observed, and the 50 mg twice daily dose was selected for the dose-expansion phase.
Efficacy Results
At a median follow-up of 11 months, casdatifan achieved an objective response rate (ORR) of 31.3% (90% CI, 16.1%-50.0%) in heavily pretreated patients. After nearly a year of treatment, one additional patient achieved a response, boosting the ORR to 34% (95% CI, 16%-50%). The median time to response was 2.8 months. The disease control rate (DCR) was 81.3% (90% CI, 63.6%-92.8%), and the median progression-free survival (PFS) had not been reached, with only 18.8% of patients experiencing progressive disease.
"Based on our experience in the ARC-20 study, we have seen casdatifan’s ability to quickly bring tumor growth under control and its high response and disease control rates," said Toni K. Choueiri, MD, director of the Lank Center for Genitourinary Oncology at Dana-Farber Cancer Institute, and lead investigator of ARC-20. "Based on these data, casdatifan has the potential to be a future treatment option for kidney cancer. I am particularly interested in planned research into novel combinations for casdatifan in both first- and second-line ccRCC."
Mechanism of Action and Pharmacokinetics
Casdatifan is an orally bioavailable small-molecule inhibitor of HIF-2α, a key driver in the development and progression of ccRCC. The agent exhibits high potency and a favorable pharmacokinetic profile, with dose-proportional exposure increases and a mean terminal half-life of approximately 18 to 24 hours. Studies in healthy volunteers showed that 50 mg twice daily dosing achieves drug exposure comparable to 100 mg once daily.
Study Design and Patient Population
The ARC-20 trial enrolled patients with ccRCC and other advanced solid tumors with measurable lesions and adequate organ function. The dose-expansion phase included ccRCC patients who had progressed on at least two prior lines of treatment, including a PD-1 inhibitor and a TKI inhibitor. In the 50 mg twice daily cohort (n = 33), the median patient age was 62 years, and 76% were male. Patients were heavily pretreated, with varying numbers of prior lines of therapy.
Tolerability and Safety
In the dose-escalation phase, the median treatment duration in the 50 mg twice daily group (n = 6) was 2 months. All patients experienced treatment-emergent adverse events (TEAEs), with 83% related to casdatifan. Common TEAEs included anemia (83%) and fatigue (50%). In the expansion phase (n = 33), 97% of patients experienced any TEAEs, and 94% were related to the study drug. Grade 3 TEAEs occurred in 45% of patients, with anemia (36%) and hypoxia (9%) being notable. These toxicities led to dose interruptions or reductions in some patients.
Additional Observations
Additional data from the dose-expansion phase indicated a trend of reduction in target lesion diameters with casdatifan treatment. In the 50 mg once daily cohort (n = 28), the ORR was 25.0% (90% CI, 10.7%-44.9%), and the DCR was 85.7% (95% CI, 67.3%-96.0%).
"These data demonstrate the therapeutic potential of casdatifan as a potential best-in-class HIF-2α inhibitor and support further development of casdatifan in ccRCC," the study authors concluded.
