Histologically or cytologically documented unresectable, locally advanced or metastatic breast cancer or gastric cancer refractory to standard therapy.
For subjects with breast cancer:
Prior treatment with trastuzumab, pertuzumab, and T-DM1, either alone or in combination, is required. Subjects with a primary tumor that is hormone (estrogen, progesterone, or both) receptor-positive or receptor-negative are eligible. Prior hormone therapy is allowed, but last dose must be at least 14 days prior to first dose of MEDI4276.
For subjects with gastric cancer:
Prior treatment with a trastuzumab containing chemotherapy regimen is required. HER2 Positive disease documented as FISH-positive and/or 3+ by IHC on previously collected tumor tissue. At least one lesion measurable by RECIST Version 1.1.
Exclusion Criteria:
Receipt of any conventional or investigational anticancer treatment within 28 days prior to the first dose of MEDI4276.
History of exposure to the following cumulative doses of anthracyclines:
Doxorubicin or liposomal doxorubicin >350 mg/m². Epirubicin >530 mg/m². Mitoxantrone >90 mg/m² and idarubicin > 70 mg/m². If another anthracycline or more than 1 anthracycline has been used, then the cumulative dose must not exceed the equivalent of 350 mg/m² of doxorubicin. Known brain metastases that are untreated, symptomatic, or require therapy to control symptoms; or any radiation, surgery or other therapy to control symptoms from brain metastases within 2 months prior to first dose of MEDI4276.
