Addition of X4P-001 to Nivolumab Treatment in Participants With Renal Cell Carcinoma

Inclusion Criteria:

Histologically confirmed diagnosis of Renal Cell Carcinoma with a documented clear cell component (ccRCC).
Currently receiving nivolumab and considered by Investigator to have the potential to derive clinical benefit from continuing treatment with nivolumab.
Based on Response Evaluation Criteria in Solid Tumors (RECIST) Version 1.1 criteria on current nivolumab treatment (prior to initiation of this study), has a best response of confirmed stable disease (SD) or confirmed progressive disease (PD). Confirmed SD or confirmed PD refers to a response that is confirmed by a second scan which is at least 4 weeks apart from the previous scan.
At least one extra-renal measurable target lesion meeting the criteria of RECIST Version 1.1.
Agree to use contraception from screening, through the study, and for at least 5 months after the last dose of nivolumab as follows: for women of childbearing potential agree to use highly-effective contraceptive methods; for males, agree to use a condom with sexual partner.

Exclusion Criteria:

Pregnant or nursing.
Life expectancy of less than 3 months.
Performance status greater than or equal to (≥) 2 (Eastern Cooperative Oncology Group [ECOG] criteria).
New York Heart Association (NYHA) Class III or IV, uncontrolled hypertension, or clinically significant arrhythmia.
Previously received X4P-001.
Has a second malignancy. Except: malignancies that were treated curatively and have not recurred within 2 years prior to study treatment; completely resected basal cell and squamous cell skin cancers; any malignancy considered to be indolent and that has never required therapy; and completely resected carcinoma in situ of any type.
Has active central nervous system (CNS) metastases (including evidence of cerebral edema by Magnetic Resonance Imaging [MRI], or progression from prior imaging study, or any requirement for steroids, or clinical symptoms of/from CNS metastases) within 28 days prior to study treatment. Subjects with known CNS metastases must have a baseline MRI scan within 28 days of study treatment.
Ongoing clinical adverse events National Cancer Institute Common Terminology Criteria for Adverse Events (NCI CTCAE) Grade greater than (>) 2 resulting from prior cancer therapies.
Known history of Human Immunodeficiency Virus (HIV) or Acquired Immunodeficiency Syndrome (AIDS); or positive test for hepatitis C virus (HCV), or hepatitis B surface antigen (HBsAg).
History of clinically significant or uncontrolled cardiac, hepatic, or pulmonary disease.
Has had within the past 6 months the occurrence of one or more of the following events: myocardial infarction, cerebrovascular accident, deep vein thrombosis, pulmonary embolism, hemorrhage (NCI CTCAE Grade 3 or 4), chronic liver disease (meeting criteria for Child-Pugh Class B or C), or organ transplantation.
Inadequate hematologic, hepatic, or renal function.