Response to guadecitabine (SGI-110) combined with cisplatin and gemcitabine (GCG) in platinum refractory germ cell tumors (GCTs).

Abstract

e17057 Background: Treatment options for platinum refractory GCTs are limited. Platinum resistance derives, in part, from tumour suppressor gene promotor methylation. In vitro, this reverses on co-administration of a DNA hypomethylating agent. Guadecitabine is a next generation hypomethylating agent. SPIRE is a phase Ib/IIa clinical trial to establish a GCG dose/schedule. Methods: We report 2 platinum refractory GCT patients (pts) treated (txd) in SPIRE with GCG (guadecitabine 20 mg/m2, SC, day (D) 1-5; cisplatin 70 mg/m2, IV, D8; gemcitabine 1000 mg/m2, IV, D8 + 15; filgrastim 300 μg, SC, D15-21; q21). Results: Pt 1: 21 yo man, testicular mixed GCT (seminoma/malignant teratoma intermediate). Prior tx: 2001, orchidectomy; 2005, 3 x BEP (bleomycin, etoposide, cisplatin) + retroperitoneal lymph node dissection. 2015, 2 x TI (paclitaxel, ifosfamide), 3 x TIP (cisplatin, ifosfamide, paclitaxel); 2016, 3 x HDCE (high dose carboplatin/ etoposide + autologous stem cell transplantation); 2017, 6 x GOP (gemcitabine, oxaliplatin, paclitaxel). In 2017, received 6 x GCG in SPIRE for CT confirmed lung metastases (mets) and rising β-hCG (human chorionic gonadotropin). Response: RECIST stable disease with metabolic CR on PET in lungs and > 90% β-hCG reduction. In Cycle 6, pt developed symptomatic brain mets, treated with WBRT (40Gy, 20#) + cyberknife to the six mets completed 2018. Since 2018, ongoing complete marker and radiologic (brain and systemic) remission (20 months). Pt 2: 44 yo man, primary mediastinal non-seminomatous GCT. Prior tx: 2008, 4 x BEP + mediastinal mass resection; 2015, 4 x TIP; 2016, 1 x HDCE. In 2017, received 5 x GCG in SPIRE for a PET avid mediastinal/pulmonary relapse and AFP (alpha-fetoprotein) rise. Response: RECIST stable and > 50% AFP reduction for 6 months (subsequent progression with intracerebral metastasis). Treatment was well tolerated. Grade 4 neutropenia/ thrombocytopenia occurred in both and febrile neutropenia in pt 1. Both required a 25% dose reduction in Cis/Gem. Conclusions: GCG produced exceptional clinical responses in both platinum refractory GCT pts. Prospective evaluation is warranted. Clinical trial information: 16332228.