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531 A Phase 1b multi-tumor cohort study of cabozantinib plus atezolizumab in advanced solid tumors: results of the triple-negative breast cancer, ovarian cancer, and endometrial cancer cohorts
  1. Ira Winer1,
  2. Akhila Wimalasingham2,
  3. Joaquina Baranda3,
  4. Armando Santoro4,
  5. Kristen Spencer5,
  6. Capucine Baldini6,
  7. Linda Duska7,
  8. Vivek Subbiah8,
  9. Sandip Patel9,
  10. Polina Khrizman10,
  11. Griet Van Lancker11,
  12. Lana Andrianova12,
  13. Sumandeep Atwal12,
  14. Keerti Sharma12 and
  15. Luis Manso13
  1. 1Karmanos Cancer Institute, Detroit, MI, USA
  2. 2Queen Mary University of London, London, UK
  3. 3University of Kansas Cancer Center, Kansas City, KS, USA
  4. 4Humanitas University, IRCCS, Rozzano-Milan, Italy
  5. 5Rutgers Cancer Institute of New Jersey, New Brunswick, NJ, USA
  6. 6DITEP, Gustave Roussy, Villejuif, France
  7. 7University of Virginia, Charlottesville, VA, USA
  8. 8The University of Texas MD Anderson Cancer Center, Houston, TX, USA
  9. 9University of California San Diego, La Jolla, CA, USA
  10. 10MD Anderson Cancer Center at Cooper, Camden, NJ, USA
  11. 11Ghent University, Ghent, Belgium
  12. 12Exelixis, Inc., Alameda, CA, USA
  13. 13Hospital Universitario 12 de Octubre, Madrid, Spain


Background Cabozantinib, a multiple receptor tyrosine kinase inhibitor, promotes an immune-permissive environment which might enhance the activity of immune checkpoint inhibitors. COSMIC-021 (NCT03170960), a multicenter phase 1b study, is evaluating the combination of cabozantinib with atezolizumab in advanced solid tumors; here we present efficacy and safety results in patients with triple negative breast cancer (TNBC), ovarian cancer (OC), and endometrial cancer (EC).

Methods Eligible patients had locally advanced or metastatic TNBC, OC, or EC and had radiographically progressed on prior systemic anticancer therapy. One or two lines of prior therapy were permitted. Patients with OC were platinum resistant or refractory. Prior treatment with anti-PD-1 or anti-PD-L1 agents was allowed for patients with TNBC. Patients received cabozantinib, 40 mg PO QD, plus atezolizumab, 1200 mg IV Q3W. The primary endpoint was objective response rate (ORR) per RECIST 1.1 as assessed by investigator. Other endpoints included safety, duration of response (DOR), progression free survival (PFS), and overall survival (OS). CT/MRI scans were performed Q6W for the first year and Q12W thereafter.

Results As of February 19, 2021, 30–32 patients were enrolled in each of the cohorts. 47% of patients with TNBC, 47% with OC, and 40% with EC had received 2 lines of prior therapy. Median follow-up was 18.7 months, 20.8 months, and 19.0 months for the TNBC, OC, and EC cohorts, respectively. Grade 3/4 treatment-related adverse events occurred in 33% of patients with TNBC, 56% with OC, and 37% with EC. One Grade 5 treatment-related adverse event of pulmonary hemorrhage occurred in the TNBC cohort and one of encephalitis occurred in the OC cohort. Cabozantinib plus atezolizumab demonstrated clinical activity in all three tumor cohorts (table 1).

Abstract 531 Table 1

Conclusions Cabozantinib in combination with atezolizumab demonstrated encouraging clinical activity in patients with previously treated advanced cancers.

Acknowledgements Medical writing support provided by Suvajit Sen, PhD (Exelixis, Inc.)

Trial Registration NCT03170960

Ethics Approval Yes

Consent Yes

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