A Study of LY3321367 Alone or With LY3300054 in Participants With Advanced Relapsed/Refractory Solid Tumors

Inclusion Criteria: * For Ph1a monotherapy and combination cohorts, histologic or cytologic confirmation of advanced solid tumor. * For Phase 1a and 1b, prior PD-1 or PD-L1 therapy or other immunotherapy is allowed, if the following criteria are met: * Must not have experienced a toxicity that led to permanent discontinuation of prior immunotherapy. * Must have completely recovered or recovered to baseline prior to screening from any prior AEs occurring while receiving prior immunotherapy. * Must have provided tumor tissue sample, as follows: * For participants entering Ph1a: have submitted, if available, an archival tumor tissue sample. * For participants entering Ph1b: have submitted, a sample from a newly obtained core or excisional biopsy of a tumor lesion or a recent biopsy defined by 6 months of study enrollment (Ph1b). * Must have a performance status of 0 to 1 on the Eastern Cooperative Oncology Group (ECOG) scale. * Must have adequate organ function. * Have an estimated life expectancy of 12 weeks, in judgement of the investigator. Exclusion Criteria: * Have symptomatic or uncontrolled brain metastases, spinal cord compression, or leptomeningeal disease requiring concurrent treatment, including but not limited to surgery, radiation, and/or corticosteroids (participants receiving anticonvulsants are eligible). * Have received a live vaccine within 30 days before the first dose of study treatment. * If female, is pregnant, breastfeeding, or planning to become pregnant. * Have a history or current evidence of any condition, therapy, or laboratory abnormality that might interfere with the participant's participation. * Have moderate or severe cardiovascular disease. * Have a serious concomitant systemic disorder that would compromise the participant's ability to adhere to the protocol, including active or chronic infection with human immunodeficiency virus (HIV), active hepatitis B virus (HBV), active hepatitis C virus (HCV), active autoimmune disorders, or prior documented severe autoimmune or inflammatory disorders requiring immunosuppressive treatment. * Use of escalating or chronic supraphysiologic doses of corticosteroids or immunosuppressive agents (such as, cyclosporine). \[Use of topical, ophthalmic, inhaled, and intranasal corticosteroids permitted\]. * Bowel obstruction, history or presence of inflammatory enteropathy or extensive intestinal resection. * Evidence of interstitial lung disease or noninfectious pneumonitis.