A phase 2 single-arm study of cabozantinib in patients with advanced or unresectable renal cell carcinoma pretreated with one immune checkpoint inhibitor: The BREAKPOINT trial (MeetUro trial 03-NCT03463681).
Authors: Procopio Giuseppe , Claps Melanie , Pircher Chiara , Porcu Luca , Sepe Pierangela , Guadalupi Valentina , De Giorgi Ugo , Lolli Cristian , Maruzzo Marco , Nole Franco , Iacovelli Roberto , Masini Cristina , Baldessari Cinzia , Doni Laura , Cusmai Antonio , Gernone Angela , Scagliarini Sarah , Pignata Sandro , De Braud Filippo G. , Verzoni Elena 
Published: June 2021

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Background: For many years, vascular endothelial growth factor (VEGF)-targeted therapy (tp) has been a milestone for metastatic renal cell carcinoma (mRCC). Recently, first line tp based on anti-PD-1/PD-L1 immune-checkpoint inhibitors (ICIs) plus tyrosine-kinase-inhibitors (IO-TKI) and anti-PD-1 plus anti-CTLA-4 combos (IO-IO) significantly improved survival of mRCC patients (pts). Prospective data are lacking to determine the efficacy of anti-VEGF tp after IO-IO or IO-TKI. Cabozantinib (Cabo) showed to prolong survival in mRCC pts pre-treated with TKIs and to target kinases involved in immune-escape. So, it may represent an ideal agent to be used sequentially after ICIs. Methods: This is an open label, single arm, multicenter, phase II study evaluating efficacy and safety of Cabo in mRCC pts who received an anti-PD-1/PD-L1-based adjuvant (adj) or first line tp. Cabo 60 mg/daily was administered until progressive disease (PD) or unacceptable toxicity. Primary endpoint was progression free survival (PFS) by Brookmeyer-Crowley test, secondary endpoints were overall survival (OS), objective response rate (ORR) and safety. Exploratory endopoints were to investigate tissue PD-L1 expression, to assess the modulating activity of Cabo on local and systemic tumor immunity and to explore bone formation and reabsorption markers. Results: From July 2018, 49 pts were enrolled and 48 were included in the analysis. Median age was 62.5 years (range: 30-78), 63% of pts were male. At baseline, 26% of pts had a good Heng risk score, 47% intermediate and 28% a poor risk, while in 2% of pts the class of risk was undetermined. 74% of pts received an IO-IO combo as first line tp, 17% IO-TKI, 9% pts an adj IO monotherapy. Pts received a median of 10 cycles of Cabo (range 5-17 cycles). 25 pts (53%) are still on tp, 1 patient discontinued Cabo for AEs, 13 pts for radiological PD, 6 pts discontinued for clinical PD or death, while 2 pts for reasons other than AEs or PD. Among evaluable cases, 17 pts (43%) achieved a partial response and 15 pts (37%) stable disease. Complete responses were not observed. At a median (m) follow-up of 8.0 months (mo) (4.4-13.5 mo), 71% of pts were alive and mPFS was 9.3 mo (95% CI 7.1-29.0 mo). Grade (G) 3-4 adverse events (AEs) occurred in 34% of pts, including more frequently serum bilirubin increase, hypertension, calcium and sodium serum levels alterations and oral mucositis. G1-2 were observed in 61% of pts, including in most of cases diarrhoea, nausea, oral mucositis, disgeusia, hand-foot syndrome, fatigue and hypothyroidism. Due to AEs, transitory withholding of Cabo was observed in 53.5% of pts and for 23 pts (48%) dose reductions were needed. Conclusions: So far, Cabo tp after IO-IO or IO-TKI showed promising results and was well tolerated. Longer follow-up is needed for final OS and exploratory endpoints results. Clinical trial information: NCT03463681.