Study of DS-8201a in Subjects With Advanced Solid Malignant Tumors

Objective response rate (ORR) by independent central review was defined as the proportion of participants who achieve either complete response [CR] or partial response [PR] per Response Evaluation Criteria in Solid Tumors (RECIST) v1.1. CR was defined as a disappearance of all target lesions and PR was defined as at least a 30% decrease in the sum of diameters of target lesions. HER2-positive other solid tumors included participants with salivary/submandibular/parotid gland (8 participants), breast with HER2-mutation (2 participants), endometrial (2 participants), esophageal (2 participants), Paget's disease (2 participants), cholangiocarcinoma (1 participant), extraskeletal myxoide chondrosarcoma (1 participant), gallbladder (1 participant), pancreatic (1 participant), small intestine (1 participant), uterine cervix (1 participant) and HER2-low gastric/GEJ (1 participant who received 5.4 mg/kg) cancer.

Disease control rate (DCR) by independent central review was calculated as the proportion of participants demonstrating complete response (CR), partial response (PR), or stable disease (SD) for a minimum of 6 weeks (±1week) from the first dosing date. CR was defined as a disappearance of all target lesions, PR as at least a 30% decrease in the sum of diameters of target lesions, and stable disease (SD) was defined as neither sufficient shrinkage to qualify for PR nor sufficient increase to qualify for progressive disease (PD; at least a 20% increase in the sum of diameters of target lesions. HER2-positive other solid tumors included 8 participants with salivary/submandibular/parotid gland, 2 breast with HER2-mutation, 2 endometrial, 2 esophageal, 2 Paget's disease, 1 cholangiocarcinoma, 1 extraskeletal myxoide chondrosarcoma, 1 gallbladder, 1 pancreatic, 1 small intestine, 1 uterine cervix, and 1 participant who received 5.4 mg/kg with HER2-low gastric/GEJ cancer.

Best overall response by independent central review was defined as the proportion of participants who achieved either complete response [CR], partial response [PR], stable disease (SD), progressive disease (PD), or were non-evaluable (NE) as per RECIST v1.1. CR was defined as a disappearance of all target lesions, PR at least a 30% decrease in the sum of diameters of target lesions, and SD as neither sufficient shrinkage to qualify for PR nor sufficient increase to qualify for PD defined as at least a 20% increase in the sum of diameters of target lesions. HER2-positive other solid tumors included 8 participants with salivary/submandibular/parotid gland, 2 breast with HER2-mutation, 2 endometrial, 2 esophageal, 2 Paget's disease, 1 cholangiocarcinoma, 1 extraskeletal myxoide chondrosarcoma, 1 gallbladder, 1 pancreatic, 1 small intestine, 1 uterine cervix, and 1 participant who received 5.4 mg/kg with HER2-low gastric/GEJ cancer.

Duration of response (DoR) by independent central review was defined as the time between the date of the first complete response (CR) or partial response (PR) until the date of the first documentation of progressive disease (PD) or death due to any cause. CR was defined as a disappearance of all target lesions, PR as at least a 30% decrease in the sum of diameters of target lesions, and PD as at least a 20% increase in the sum of diameters of target lesions. HER2-positive other solid tumors included participants with salivary/submandibular/parotid gland (8 participants), breast with HER2-mutation (2 participants), endometrial (2 participants), esophageal (2 participants), Paget's disease (2 participants), cholangiocarcinoma (1 participant), extraskeletal myxoide chondrosarcoma (1 participant), gallbladder (1 participant), pancreatic (1 participant), small intestine (1 participant), uterine cervix (1 participant) and HER2-low gastric/GEJ (1 participant who received 5.4 mg/kg) cancer.

Time to response (TTR) by independent central review was defined as the time interval between the date of registration until the date at which the criteria were first met for complete response (CR) or partial response (PR). Only participants who achieved CR or PR were included in the TTR analysis. CR was defined as a disappearance of all target lesions and PR was defined as at least a 30% decrease in the sum of diameters of target lesions. HER2-positive other solid tumors included participants with salivary/submandibular/parotid gland (8 participants), breast with HER2-mutation (2 participants), endometrial (2 participants), esophageal (2 participants), Paget's disease (2 participants), cholangiocarcinoma (1 participant), extraskeletal myxoide chondrosarcoma (1 participant), gallbladder (1 participant), pancreatic (1 participant), small intestine (1 participant), uterine cervix (1 participant) and HER2-low gastric/GEJ (1 participant who received 5.4 mg/kg) cancer.

Progression-free survival (PFS) by independent central review was defined as the time from the date of enrollment to the earlier of the dates of the first objective documentation of disease progression (as per RECIST v1.1) or death due to any cause. Progressive disease was defined as at least a 20% increase in the sum of diameters of target lesions. HER2-positive other solid tumors included participants with salivary/submandibular/parotid gland (8 participants), breast with HER2-mutation (2 participants), endometrial (2 participants), esophageal (2 participants), Paget's disease (2 participants), cholangiocarcinoma (1 participant), extraskeletal myxoide chondrosarcoma (1 participant), gallbladder (1 participant), pancreatic (1 participant), small intestine (1 participant), uterine cervix (1 participant) and HER2-low gastric/GEJ (1 participant who received 5.4 mg/kg) cancer.

Overall survival (OS) by independent central review was defined as the time interval from the date of enrollment to the date of death from any cause. HER2-positive other solid tumors included participants with salivary/submandibular/parotid gland (8 participants), breast with HER2-mutation (2 participants), endometrial (2 participants), esophageal (2 participants), Paget's disease (2 participants), cholangiocarcinoma (1 participant), extraskeletal myxoide chondrosarcoma (1 participant), gallbladder (1 participant), pancreatic (1 participant), small intestine (1 participant), uterine cervix (1 participant) and HER2-low gastric/GEJ (1 participant who received 5.4 mg/kg) cancer.

The serum PK parameters of DS-8201a and its analytes for area under the concentration-versus-time curve from time 0 to the last quantifiable concentration as calculated by the linear-up log-down trapezoidal method (AUClast) and AUC from time 0 to infinity (AUCinf) elimination rate constant associated with the terminal phase were estimated using standard non-compartmental methods.

The serum PK parameters Maximum (peak) Observed serum concentration of DS-8201a and its analytes were estimated using standard non-compartmental method.

The serum PK parameters of Time of maximum plasma concentration (Tmax) for DS-8201a and its analytes were estimated using standard non-compartmental methods.

The serum PK parameters of Terminal elimination half-life for DS-8201a and its analytes was estimated using standard non-compartmental methods.

Treatment-emergent adverse events were graded by Common Terminology Criteria for Adverse Events, v4.03.