Key Inclusion Criteria:

          -  Subject has Eastern Cooperative Oncology Group (ECOG) performance status 0-1.

          -  Subjects who received prior immune-stimulatory antitumor agents, such as anti-PD-1,
             anti-PD-L1, anti-CTLA-4, OX-40, CD137, etc. are eligible.

          -  Histologically or cytologically confirmed, locally advanced or metastatic solid
             malignancy and has exhausted all the available standard therapy or is not a candidate
             for the available standard therapy.

        Select Tumor Types (COM701 monotherapy cohort expansion; COM701 in combination with
        nivolumab):

          -  Breast cancer (TNBC): Histologically confirmed incurable, advanced estrogen receptor-,
             progesterone receptor-, and human epidermal growth factor receptor 2 (HER2)-negative
             (triple-negative) adenocarcinoma of the breast, as defined by the American Society of
             Clinical Oncology-College of American Pathologists (ASCO-CAP) guidelines. Disease
             recurrence or progression during or after at least one systemic treatment that
             included an anthracycline and/or a taxane in the neoadjuvant, adjuvant, or metastatic
             setting. Subjects must have progressed after a poly ADP-ribose polymerase (PARP)
             inhibitor for patients with deleterious or suspected deleterious germline breast
             cancer susceptibility gene (BRCA) mutated metastatic breast cancer. P1b COM701 +
             nivolumab expansion cohort, COM701 monotherapy expansion cohort.

          -  Endometrial cancer: Subjects with locally advanced or metastatic endometrial cancer,
             disease recurrence or progression during or after prior therapy that included
             platinum-based chemotherapy. P1b COM701 + nivolumab expansion cohort, COM701
             monotherapy expansion cohort.

          -  Ovarian cancer: Disease recurrence or progression during or after prior therapy that
             included: surgical resection, platinum agent, PARP inhibitor (for subjects with
             deleterious or suspected deleterious germline BRCA-mutated advanced ovarian cancer or
             as a maintenance therapy for subjects who have had complete or partial response to
             platinum-based therapy). P1b COM701 + nivolumab expansion cohort, COM701 monotherapy
             expansion cohort.

          -  NSCLC: Documented stage IIIB or IV or recurrent NSCLC, Disease recurrence or
             progression during or after prior treatment that included: platinum agent, targeted
             therapy such as a TKI (if with biopsy-confirmed cytogenetic mutation eg EGFR, ROS,
             BRAF). COM701 monotherapy expansion cohort.

          -  CRC (microsatellite stable, KRAS mutation) - P1b COM701 + nivolumab expansion cohort,
             COM701 monotherapy expansion cohort.

          -  For Phase 1a monotherapy expansion and Phase 1b only: subject has at least one
             measurable lesion that could be followed during the study according to RECIST v1.1.

        Key Exclusion Criteria:

          -  Active autoimmune disease requiring systemic therapy in the last 2 years prior to the
             first dose of COM701.

          -  Symptomatic interstitial lung disease or inflammatory pneumonitis.

          -  History of immune-related events that lead to immunotherapy treatment discontinuation.

          -  Untreated or symptomatic central nervous system (CNS) metastases.

          -  Impaired cardiac function or clinically significant cardiac disease, including any of
             the following: a) Unstable angina pectoris ≤ 6 months prior to first scheduled dose of
             COM701; b) Acute myocardial infarction ≤ 6 months prior to first scheduled dose of
             COM701.