A Study of TransCon TLR7/8 Agonist With or Without Pembrolizumab in Patients With Advanced or Metastatic Solid Tumors

Inclusion Criteria: * At least 18 years of age. * Participants must have histologically confirmed locally advanced, recurrent or metastatic solid tumor malignancies that cannot be treated with curative intent (surgery or radiotherapy). * Participants must have progressed on or be intolerant of available standard of care treatment options or have disease for which there is no standard of care treatment available, with the exception of participants enrolling to the neoadjuvant cohorts. * At least 2 lesions of measurable disease, unless specified otherwise in the selection criteria. * Willingness to undergo biopsies. * Demonstrated adequate organ function within 28 days of Cycle 1 Day 1 (C1D1). * Life expectancy \>12 weeks as determined by the Investigator. * Eastern Cooperative Oncology Group (ECOG) performance status 0, 1, or 2. * Participants who have undergone treatment with anti-PD-1, anti-PD-L1, or antiCTLA 4 antibody must have at least 4 weeks from the last dose of antibody and evidence of disease progression per investigator assessment before enrollment. * Participants who have previously received an immune checkpoint inhibitor prior to enrollment must have any immune related toxicities resolved to ≤Grade 1 or baseline (prior to the checkpoint inhibitor) to be eligible. * Female and male participants of childbearing potential who are sexually active must agree to use highly effective methods of contraception. Exclusion Criteria: * Participants who have been previously…