Key Inclusion Criteria:

   1. Subjects with advanced or relapsed/refractory melanoma, ovarian cancer, NSCLC,
   colorectal cancer, pancreatic cancer, breast cancer, gastric/esophagogastric junction
   (EGJ) cancer, head and neck cancer, or urothelial cancer who have failed prior
   therapies.

   a. Subjects with melanoma, NSCLC, head and neck cancer, urothelial cancer, or mMSI-H
   or dMMR colorectal cancer must have had prior anti-PD-(L)1 pathway therapy and been
   deemed resistant (had progression on therapy or within 3 months of discontinuation of
   therapy).

   2. Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1.

   3. Subject has disease that is measurable by Response Evaluation Criteria in Solid Tumors
   (RECIST) v.1.1.

   4. Adequate bone marrow, coagulation, renal function, and liver function as determined by
   laboratory tests

Key Exclusion Criteria:

   1. For cohorts receiving E-602 and cemiplimab combination therapy:

      1. Prior moderate or severe hypersensitivity to cemiplimab or its formulation

      2. History of severe (≥ Grade 3) autoimmune complications or discontinuation due to
      toxicity following treatment with an anti-PD-(L)1 pathway therapy as a
      monotherapy, with the exception of asymptomatic Grade 3 elevations in lipase
      and/or amylase not associated with clinical manifestations of pancreatitis.

      3. Subject has an active autoimmune disease. The following are not exclusionary:
      vitiligo, type 1 diabetes, autoimmune endocrinopathies that are stable on hormone
      replacement therapy, or psoriasis that does not require systemic treatment.

      4. Previously received idelalisib.

   2. History of age-related macular degeneration (AMD).

   3. Recent surgery, treatment with another investigational agent, active infection,
   non-healing wound or uncontrolled bleeding/bleeding diathesis.

   4. Received a vaccine or prior radiotherapy within 14 days prior to Cycle 1 Day 1.

   5. Prior history of interstitial lung disease that required steroids or ≥ Grade 2
   immune-related pneumonitis or has current non-infectious pneumonitis or interstitial
   lung disease. Subject has a history of ≥Grade 3 radiation pneumonitis, or Grade 2
   radiation pneumonitis that has been active within the last 6 months.

   6. Untreated brain metastases.

   7. A known primary malignancy that is progressing or has required active treatment within
   the past 3 years.

   8. Subject is taking the equivalent of >10 mg/day oral prednisone or on systemic
   immunosuppressive therapy.

   9. Subject has had an allogeneic tissue or organ transplantation.

10. History of thromboembolic event unless the event occurred > 6 months from Cycle 1 Day
   1 and the subject is on anti-coagulation treatment.