P3.02c-001 Phase I Study of Salazosulfapyridine Targeting Cancer Stem Cells in Combination with CDDP and Pemetrexed for Chemo-Naïve Advanced Non-Sq NSCLC: Topic: Targeted Therapy

Abstract

Variant splicing isoforms of CD44 (CD44v) are a marker of cancer stem cells (CSCs) in solid tumors. CD44v stabilizes the glutamate-cystine transporter subunit xCT and thereby promotes synthesis of the intracellular antioxidant glutathione and protects CSCs from oxidative stress. Salazosulfapyridine (SASP) is an inhibitor of xCT activity, and, in combination with cisplatin (CDDP), it attenuates the increase in the proportion of CD44v-positive tumor cells during the growth of tumor xenografts in mice. Individuals with advanced (stage IIIB or IV) nonsquamous non–small cell lung cancer are eligible to enroll in a phase I dose-escalation study (standard 3+3 design) of SASP in combination with CDDP and pemetrexed (PEM) as first-line treatment. Patients receive SASP daily as well as CDDP (75 mg/m2) and PEM (500 mg/m2) on day 1 of a 21-day cycle. The primary end point is the percentage of patients who experience dose-limiting toxicity (DLT) between administration of the first dose of SASP (day 1) and day 21. From April 2015 to January 2016, 15 patients were enrolled in the study (mean age, 64 years; age range, 42–74 years; male/female ratio, 10/5; ECOG performance status 0/1 ratio, 6/9). Immunohistochemical staining of tumor biopsy specimens revealed that the proportion of CD44v-positive cells was >10% in 9 patients before SASP treatment. No DLT was observed in the first three patients treated at SASP dose level 1 (500 mg TID) or those treated at dose level 2 (1000 mg TID). At dose level 3 (1500 mg TID), two of three patients experienced a DLT (anorexia of grade 3). We enrolled additional patients at dose level 2 and two of the total of five patients treated at this dose level experienced DLTs (hypotension or pneumonitis, each of grade 3). To confirm the safety of dose level 1, we enrolled additional patients at this dose level and one of the total of six patients treated at this dose level experienced DLTs (AST and ALT elevation, each of grade 3). Exposure of SASP following oral administration varied markedly among individuals according to ABCG2 and NAT2 genotypes as previously reported. SASP 500 mg TID was the recommended dose when administered with CDDP plus PEM.