A Study of LY3415244 in Participants With Advanced Solid Tumors

Inclusion Criteria:

* For Phase 1a/b, histologic or cytologic confirmation of advanced solid tumor.
* For Phase 1a/b, biopsy of tumor samples are required. Newly obtained core or excisional biopsy of a tumor lesion prior to study enrollment and undergo a biopsy procedure during the study.
* Phase 1a, prior anti-PD-1 or anti-PD-L1 therapy or other immunotherapy is allowed.
* Phase 1b, prior anti-PD-1 or anti-PD-L1 therapy is required where anti-PD-1 or anti-PD-L1 is standard of care in respective tumor types if the following criteria are met:

  * Must not have experienced a toxicity that led to permanent discontinuation of prior immunotherapy
  * Must have completely recovered to baseline level prior to screening from any adverse events (AEs) that occurred from receiving prior immunotherapy
  * Must not have experienced a Grade ≥3 immune-related AE or immune related neurologic or ocular AE, pneumonitis or cardiomyopathy of any grade while receiving prior immunotherapy
  * Must not have required immunosuppressive agent, other than corticosteroids for the management of an adverse event and not currently require maintenance doses of \>10 milligrams (mg) prednisone (or equivalent) per day
* Must have at least 1 measurable lesion as defined by the Response Evaluation Criteria in Solid Tumors (RECIST 1.1).
* Have adequate organ function.
* Have an estimated life expectancy ≥12 weeks, in the judgement of the investigator.

Exclusion Criteria:

* Have symptomatic central nervous system (CNS) malignancy or metastasis not requiring concurrent treatment, including but not limited to surgery, radiation, corticosteroids and/or anticonvulsants to treat CNS metastases, and their disease is asymptomatic and radiographically stable for at least 30 days.
* 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 known 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.