Efficacy and Safety of Atezolizumab Plus Bevacizumab Following Disease Progression on Atezolizumab or Sunitinib Monotherapy in Patients with Metastatic Renal Cell Carcinoma in IMmotion150: A Randomized Phase 2 Clinical Trial

Background: The use of immune checkpoint inhibitors combined with vascular endothelial growth factor (VEGF)-targeted therapy as second-line treatment for metastatic clear cell renal cancer (mRCC) has not been evaluated prospectively.

Objective: To evaluate the efficacy and safety of atezolizumab + bevacizumab following disease progression on atezolizumab or sunitinib monotherapy in patients with mRCC.

Design, setting, and participants: IMmotion150 was a multicenter, randomized, open-label, phase 2 study of patients with untreated mRCC. Patients randomized to the atezolizumab or sunitinib arm who had investigator-assessed progression as per RECIST 1.1 could be treated with second-line atezolizumab + bevacizumab.

Intervention: Patients received atezolizumab 1200 mg intravenously (IV) plus bevacizumab 15 mg/kg IV every 3 wk following disease progression on either atezolizumab or sunitinib monotherapy.

Outcome measurements and statistical analysis: The secondary endpoints analyzed during the second-line part of IMmotion150 included objective response rate (ORR), progression-free survival (PFS), and safety. PFS was examined using Kaplan-Meier methods.

Results and limitations: Fifty-nine patients in the atezolizumab arm and 78 in the sunitinib arm were eligible, and 103 initiated second-line atezolizumab + bevacizumab (atezolizumab arm, n = 44; sunitinib arm, n = 59). ORR (95% confidence interval [CI]) was 27% (19-37%). The median PFS (95% CI) from the start of second line was 8.7 (5.6-13.7) mo. The median event follow-up duration was 19.4 (12.9-21.9) mo among the 25 patients without a PFS event. Eighty-six (83%) patients had treatment-related adverse events; 31 of 103 (30%) had grade 3/4 events. Limitations were the small sample size and selection for progressors.

Conclusions: The atezolizumab + bevacizumab combination had activity and was tolerable in patients with progression on atezolizumab or sunitinib. Further studies are needed to investigate sequencing strategies in mRCC.

Patient summary: Patients with advanced kidney cancer whose disease had worsened during treatment with atezolizumab or sunitinib began second-line treatment with atezolizumab + bevacizumab. Tumors shrank in more than one-quarter of patients treated with this combination, and side effects were manageable.