A Study to Assess the Safety and Efficacy of ASP1650, a Monoclonal Antibody Targeting Claudin 6 (CLDN6), in Male Subjects With Incurable Platinum Refractory Germ Cell Tumors

Inclusion Criteria

• A male subject with female partner(s) of child-bearing potential must agree to use contraception during the treatment period and for at least 6 months after the final study drug administration.
• Subject must not donate sperm during the treatment period and for 6 months after the final study treatment administration.
• A male subject with a pregnant or breastfeeding partner(s) must agree to remain abstinent or use a condom for the duration of the pregnancy or time partner is breastfeeding throughout the study period and for 6 months after the final study treatment administration.
• Subject agrees not to participate in another interventional study while receiving study drug in present study.

Disease Specific Criteria:

• Subject has histological evidence of germ cell tumor.
• Subject must have a germ cell tumor that is not amenable to cure with either surgery or chemotherapy.
• Subjects with seminoma and non-seminoma are eligible.
• Subject must have received initial cisplatin based combination chemotherapy AND demonstrated progression following at least 1 salvage regimen for advanced germ cell neoplasm (including relapsed primary mediastinal nonseminomatous germ cell tumor).
• Initial cisplatin based combination therapy includes bleomycin-etoposide-cisplatin, cisplatin-etoposide, etoposide-ifosfamide-cisplatin or similar regimens.
• "Salvage" regimens include high dose chemotherapy, paclitaxel-ifosfamide-cisplatin, vinblastine-ifosfamide cisplatin or similar regimens
• "Failure" of prior therapy is defined as: A > 25% increase in the products of perpendicular diameters of measurable tumor masses during prior therapy, which are not amenable to surgical resection; OR the presence of new tumor that are not amenable to surgical resection; OR an increase in alpha-fetoprotein (AFP) or beta human chorionic gonadotropin (βhCG) (≥ 50% increase in 2 separate samples collected at least 1 week apart are required if rising tumor markers are the only evidence of failure). NOTE: Subjects with clinically growing teratoma (enlarging mature teratoma arising during or after chemotherapy for a non seminomatous germ-cell tumor and with normal serum levels of AFP and βhCG) should undergo surgical resection if feasible.
• Subjects with late relapse (> 2 years) not amenable to resection are eligible.
• Subjects must have evidence of recurrent or metastatic carcinoma by 1 or more of the following:
• Subject has measurable disease according to Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 within 28 days prior to the first dose of study treatment. For subjects with only 1 measurable lesion and prior radiotherapy, the lesion must be outside the field of prior radiotherapy or must have documented progression following radiation therapy.
• Subject has a baseline rising tumor marker (AFP or βhCG). NOTE: If a rising tumor marker is the only evidence of progressive disease, at least 2 consecutive rising values at least 1 week apart are needed. Subjects with only evidence of disease as rising tumor marker AFP and βhCG will be assessed for alternate causes of increased serum levels of these markers, such as cross reaction with luteinizing hormone (LH) (can be tested if needed by testosterone suppression of LH), hepatitis, use of marijuana or second primary tumor.

Physical or Laboratory Findings:

• Subject must have an available tumor specimen in a tissue block or unstained serial slides, or subject is an appropriate candidate for tumor biopsy and is amenable to undergoing a tumor biopsy during the screening period.
• Subject has Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 2.
• Subject must meet all of the following criteria based on the centrally analyzed laboratory tests within 14 days prior to the first dose of study treatment. If repeat screening labs are required, local laboratory results can be used to confirm eligibility. In case of multiple central laboratory data within this period, t