This is an open-label, non-randomized, multicenter, dose-escalation and expansion study in patients with selected solid tumors.

This study will determine the safety, tolerability and activity of CDX-527.

Eligible patients that enroll to the dose-escalation portion of the study will be assigned to one of several dose levels of CDX-527. The dose-escalation part of the study will determine the safety profile of CDX-527 and determine which dose(s) of CDX-527 will be studied in the expansion part of the study.

The expansion part of the study will enroll eligible patients with certain solid tumors to be treated at dose(s) identified during dose-escalation

Up to 40 patients will be enrolled. All patients enrolled in the study will be closely monitored to determine if there is a response to the treatment as well as for any side effects that may occur.

Key Inclusion Criteria:

1. Recurrent, locally advanced or metastatic solid tumor cancer excluding the following: MSI-low colorectal cancer, glioblastoma multiforme, prostate cancer, pancreatic cancer, mucosal and ocular melanoma.
2. Receipt of all standard therapies for the tumor type
3. Measurable (target) disease by iRECIST
4. If of childbearing potential (male or female), agrees to practice an effective form of contraception during study treatment and for at least 3 months following last treatment
5. Willingness to undergo a pre-treatment and on-treatment biopsy, if required

Key Exclusion Criteria:

1. History of severe hypersensitivity reactions to other monoclonal antibodies.
2. Previous treatment with any anti-CD27 antibody.
3. Inadequate washout period from prior therapy as defined in the Protocol.
4. Patients who have received more than 0 or 1 prior PD-1/PD-L1 inhibitor depending on their tumor type
5. Major surgery within 4 weeks prior to study treatment.
6. Use of immunosuppressive medications within 4 weeks or systemic corticosteroids within 2 weeks prior to study treatment.
7. Other prior malignancy, except for adequately treated basal or squamous cell skin cancer or in situ cancers. For all other cancers, the patient must be disease-free for at least 3 years to be allowed to enroll.
8. Thrombotic events within the last 6 months prior to study treatment
9. Active, untreated central nervous system metastases.
10. Active autoimmune disease or documented history of autoimmune disease.
11. History of (non-infectious) pneumonitis or has current pneumonitis.
12. Active diverticulitis
13. Known infection of HIV, Hepatitis B, or Hepatitis C.

There are additional criteria your study doctor will review with you to confirm your eligibility for the study.