Phase 1 Study of STRO-006 in Adults With Refractory Solid Tumors That Are Recurrent or Metastatic

Inclusion Criteria: * Histologically or cytologically documented refractory solid tumors that are recurrent or metastatic including: HNSCC (excluding EBV-positive nasopharyngeal carcinoma), NSCLC, esophageal/gastric cancer, colorectal cancer, endometrial carcinoma, urothelial carcinoma, and breast cancer (HR-positive \[HER2-positive or HER2-negative\] and TNBC subtype) * Age ≥ 18 years * Life expectancy of at least 3 months * Willingness and ability to comply with the study protocol and long * Eastern Cooperative Oncology Group (ECOG) performance status 0 to 1-term follow-up (LTFU) assessments * Has received standard systemic therapies with known clinical benefit, or is considered inappropriate for such therapies, in the opinion of the investigator. In the dose escalation Phases (Parts 1A and 1C), there is no limit on the number of prior therapies * Expansion Phase (Part 1B) only: Up to two prior therapies are allowed. For participants with AGA-driven adenocarcinoma NSCLC up to four prior therapies are allowed * Measurable disease per RECIST v1.1. * Adequate hematologic and organ function Exclusion Criteria: * Prior anticancer treatment with an ADC with a TOP1 inhibitor payload. (Prior therapy with an ITGB6-targeted ADC is otherwise allowed.) * Prior anticancer therapy (prior to first dose of study treatment): chemotherapy within ≤ 2 weeks, ICI ≤ 3 weeks, ADCs ≤ 3 weeks, palliative radiation therapy ≤ 2 weeks, and major surgery ≤ 4 weeks of C1D1. If not specified, ≥ 5 half-lives or 2 weeks, whichever is longer, since administration of prior therapy must have elapsed * Residual Common Terminology Criteria for Adverse Events (CTCAE) v5 ≥ Grade 2 toxicity from prior anticancer therapy, with the exception of Grade 2 alopecia or Grade 2 peripheral neuropathy, which is controlled, and endocrinopathies secondary to prior ICI controlled by hormonal treatment. For Part 1C only: discontinued prior immunotherapy due to treatment-related toxicity * Untreated or active brain metastases and/or leptomeningeal disease * Participants with active ILD or active, non-infectious pneumonitis or a history of active pneumonitis ≤ 6 months from the first dose of study treatment * Significant, concurrent renal, hepatic, hematological, gastrointestinal, endocrine, pulmonary, neurological, cerebral, or psychiatric disease that could impact participation in this clinical trial * Previous solid organ or bone marrow transplantation * Concurrent participation in another therapeutic treatment trial