First-in-Human Study of XMT-1592 in Patients With Ovarian Cancer and NSCLC Likely to Express NaPi2b

Inclusion Criteria: * Ability to give informed consent. * ECOG performance status 0 or 1. * Measurable disease as per RECIST, version 1.1. Resolution of all acute toxic effects of prior therapy or surgical procedures to Grade ≤1 (except alopecia). * Adequate organ function. * Confirmed availability of tumor tissue blocks or freshly cut tissue slides for NaPi2b testing. -In EXP, ability to undergo a fresh biopsy before enrollment, unless not medically feasible. * For women of childbearing potential and men with partners of childbearing potential, agreement to use a highly effective form of hormonal contraception or two effective forms of non-hormonal contraception by the patient and/or partner, and to continue the use of contraception for the duration of study treatment and for at least 6 months after the last dose of study treatment. * Histologically or cytologically confirmed solid tumors of the types specified below, with incurable, locally advanced or metastatic disease that has failed standard therapy or for which no standard treatment option exists. * Ovarian Cancer: Histological diagnosis of epithelial ovarian, fallopian tube, or primary peritoneal cancer, excluding the mucinous subtype. NSCLC: Histological diagnosis of nonsquamous NSCLC. Exclusion Criteria: * Major surgery within 28 days of starting study treatment; -or- systemic anti-cancer therapy within the lesser of 28 days or 5 half-lives of the prior therapy before starting study treatment -or- recent radiation therapy with unresolved toxicity. * Brain metastases that are: untreated, progressive, have required any type of major treatment, e.g., whole-brain radiation treatment, adjuvant chemotherapy, gamma knife, to control symptoms from brain metastases within 30 days of the first study treatment. Or any history of leptomeningeal metastasis. * Current known active infection with HIV, hepatitis B virus, or hepatitis C virus. * No prior history of liver disease such as liver cirrhosis, hepatic fibrosis * Current severe, uncontrolled systemic disease (e.g., clinically significant cardiovascular, pulmonary, or metabolic disease) or intercurrent illness that could interfere with per-protocol evaluations. * Severe dyspnea at rest due to complications of advanced malignancy, or requiring supplementary oxygen therapy. * Currently active pneumonitis or interstitial lung disease. * Pregnant or nursing women. * History of other malignancy within the last 5 years, except for appropriately treated carcinoma in situ of the cervix, non-melanoma skin carcinoma, or other malignancy with a similar expected curative outcome. * Participation in the DES component of the study. * Prior use of mirvetuximab soravtansine or another ADC containing an auristatin or maytansinoid payload.