Pazopanib (PZP) in germ cell tumors (GCT) after chemotherapy (CT) failure: Final results of the open label, single-group, phase II Pazotest trial

414 Background: Therapeutic options for patients (pts) with chemoresistant GCT are limited and prognosis is poor. PZP is a potent and selective tyrosine kinase inhibitor (TKI) with distinct antiangiogenic activity. Methods: In Pazotest trial (NCT01743482), pts were given PZP 800 mg/day until disease progression (PD) or unacceptable toxicity. Eligibility included failure of ≥ 2 platinum-based CT, including high-dose (HD)-CT. Baseline serum tumor markers (STM), computed tomography and FDG-PET were repeated after 4 wks and q8 weeks thereafter. The primary endpoint was PFS (H0: 3-m PFS ≤ 10%, H1: ≥ 25%, α = 5%/β = 20%). PD was defined as rising STM, increasing size of nonteratomatous masses (RECIST v1.1), or the appearance of new lesions. Translational analyses included circulating IL8 levels and next generation sequencing of pre-PZP tissue from extreme responders. Results: 43 pts were enrolled from 05/2013 to 07/2016. 35 pts (81.4%) had nonseminoma, 6 (14%) primary mediastinal GCT. The number of failed CT regimen was: 2 (11.6%), 3 (51.2%), > 3 (37.2%). 53.5% had failed HDCT. 39 pts had elevated STM: 56.4% AFP, 43.6% HCG. Grade 3-4 adverse events were seen in 4 pts (increased AST/ALT). 26/39 pts (66.7%) had STM reduction (38.5% > 50% from baseline) after 4 wks. RECIST results: 1 partial response, 20 stable disease, 16 PD (6 not evaluable). 12 (27.9%) had a decreased FDG uptake. Median follow-up was 29.6 months. 3-m PFS was 12.8% (95%CI: 5.7-28.9), median PFS was 2.5 m (IQR: 1.0-3.0). 24-m OS was 14.2% (95%CI: 6.0-33.7). In pts with > 50% STM decline, 24-m OS was 24.1% (95%CI: 8.3-69.6). Univariably, STM was associated with OS (HCG vs AFP: HR: 2.73, 95%CI: 1.24-6.02, p = 0.042). Baseline and +4wks IL8 levels did not predict for PFS/OS. In 2 responding pts, new mutations were found ( FLT3, G846V and RAD50 E448Q classified as damaging; TSC2, R197M and TNF A16V classified as benign). Conclusions: PZP was well tolerated and showed predictable activity, with early but short-living STM decline. Long term survival was obtained in a significant proportion of pts. Based on the present results, PZP may be investigated in earlier disease stages as an optimal bridging therapy preceding salvage curative treatment. Clinical trial information: NCT01743482.