This trial will look at a drug called sigvotatug vedotin (SGN-B6A) to find out whether it is safe for Chinese participants who have solid tumors. It will study sigvotatug vedotin to find out what its side effects are. A side effect is anything the drug does besides treating cancer. It will also study how do Chinese participants' body interact with sigvotatug vedotin.

Inclusion Criteria:

• Subjects must have histologically or cytologically confirmed metastatic or unresectable locally advanced solid malignancy within one of the tumor types listed below.

  • NSCLC
  • HNSCC
  • ESCC
  • GAC
  • EAC
  • GEJ adenocarcinoma

• Subjects must have disease that is relapsed or refractory, or be intolerant to systemic standard-of-care therapies, and in the judgement of the investigator, should have no appropriate standard-of-care therapeutic option. If a standard-of-care therapy is available that has not been administered, the reason that the therapy is not appropriate must be documented.

• Adequate organ function as defined by the baseline laboratory criteria obtained within 7 days prior to SGN-B6A initiation (Cycle 1 Day 1)

• Measurable or non-measurable disease per RECIST v1.1 at baseline.

• An Eastern Cooperative Oncology Group (ECOG) Performance Status score of 0 or 1.

Exclusion Criteria:

• History of another malignancy within 3 years before the first dose of study intervention, or any evidence of residual disease from a previously diagnosed malignancy. Exceptions are malignancies with a negligible risk of metastasis or death.

• Participants with any of the following respiratory conditions:

  • Evidence of noninfectious interstitial lung disease (ILD) or pneumonitis that:
  • * Was previous diagnosed and required systemic steroids, or
  • * Is currently diagnosed and managed, or
  • * Is suspected on radiologic imaging at screening
  • Known diffusing capacity of the lung for carbon monoxide (DLCO) < 50%
  • Any Grade greater than or equal to (≥) 3 pulmonary disease unrelated to underlying malignancy
  • Prior radiation therapy to the lung that is >30 gray (Gy) within 6 months of the first dose of sigvotatug vedotin.

• Pre-existing peripheral neuropathy Grade greater than or equal to (≥) 2

• Uncontrolled diabetes mellitus

• Known active central nervous system metastases. Participants with previously treated brain metastases may participate provided they:

  • are clinically stable for at least 4 weeks prior to study entry after brain metastasis treatment,
  • have no new or enlarging brain metastases, and
  • are off of corticosteroids prescribed for symptoms associated with brain metastases for at least 7 days prior to first dose of study drug.

• Known history or current diagnosis of carcinomatous meningitis

• Previous treatment with an MMAE-containing agent or an agent targeting integrin beta-6

• Prior anticancer therapies:

  • Chemotherapy within 21 days prior to first administration of sigvotatug vedotin
  • Targeted small molecule agents within 14 days or 5 half-lives (whichever is longer) prior to first administration of sigvotatug vedotin
  • Antibody-based anticancer or other investigational antitumor therapy within 28 days prior to first administration of sigvotatug vedotin
  • Focal radiotherapy or major surgery that is not completed 14 days prior to the first dose of sigvotatug vedotin

• Traditional or herbal medicines:

  • Anti-cancer traditional or herbal medicines within 28 days prior to first administration of sigvotatug vedotin
  • Traditional or herbal medicines for other purposes (such as supportive care) within 7 days prior to first administration of sigvotatug vedotin

Pfizer will provide access to individual de-identified participant data and related study documents (e.g. protocol, Statistical Analysis Plan (SAP), Clinical Study Report (CSR)) upon request from qualified researchers, and subject to certain criteria, conditions, and exceptions. Further details on Pfizer's data sharing criteria and process for requesting access can be found at: https://www.pfizer.com/science/clinical\_trials/trial\_data\_and\_results/data\_requests.