Parts 1 and 2 The primary purpose of this study is to understand the safety of NL-201 when given intravenously as monotherapy in patients with advanced cancer to evaluate tolerability and to identify a recommended dose and schedule for further testing. In Part 1, there will be backfill cohorts at certain Data Monitoring Committee (DMC)-cleared dose levels and schedules to collect pharmacokinetic (PK), pharmacodynamic (PD) and response data in certain tumor types or to explore additional pre-medication regimens.

Parts 3 and 4 The primary purpose of this study is to understand the safety of NL-201 in combination with pembrolizumab when both drugs are given intravenously in patients with advanced cancer, to evaluate tolerability, and to identify a recommended dose and schedule for further testing.

Patients will have tests and exams to see if they are eligible for the clinical trial.

Parts 1 and 2 If eligible, the patient will receive NL-201 treatment by vein. Tumor response to treatment will be assessed every 6 weeks for 12 weeks, and every 12 weeks thereafter until disease progression.

Patients will be able to receive study treatment as long as it is tolerated and there is evidence of clinical benefit. Safety follow-up will occur within 7 days after the last dose of NL-201. Patients will then enter long-term follow-up until starting a subsequent therapy.

In Part 1, there will be backfill cohorts at certain DMC-cleared dose levels and schedules to collect PK, PD and response data in certain tumor types or to explore additional pre-medication regimens.

Parts 3 and 4 If eligible, the patient will receive NL-201 and pembrolizumab treatment by vein. Tumor response to treatment will be assessed every 6 weeks for 12 weeks, and every 12 weeks thereafter until disease progression.

Patients will be able to receive study treatments as long as they are tolerated and there is evidence of clinical benefit. Safety follow-up will occur within 7 days after the last dose of investigational product. Patients will then enter long-term follow-up until starting a subsequent therapy.

Inclusion Criteria:

• Patients with measurable disease
• Patients with Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1
• At least 6 weeks from any prior nitrosurea or mitomycin C therapy; at least 4 weeks from any other prior chemotherapy or checkpoint inhibitor; at least 2 weeks from any kinase inhibitor
• Part 1 Only: Patients with relapsed or refractory advanced solid tumor, other than prostate cancer, who have progressed, not tolerated or are ineligible for all approved lines of therapy
• Part 2 Only: Patients with kidney and skin cancer who have failed at least 1 line of systemic therapy
• Part 3 Only: Patients with solid tumors who have received ≥ 1 prior line of therapy for advanced or metastatic disease
• Part 4 Only: Patients with diagnosed target disease OR previously received pembrolizumab

Exclusion Criteria:

• Prostate Cancer
• Any serious medical condition or laboratory abnormality or psychiatric condition or any other significant or unstable concurrent medical illness (in the opinion of the Investigator) would preclude protocol adherence or would make the safety of the study drug difficult to assess
• Known or suspected SARS-CoV-2 infection, unless patient tests negative for SARS-CoV-2 within the Screening period
• History of solid organ transplant or bone marrow transplant
• Prior chimeric antigen receptor T-cell (CAR-T) or allogeneic cellular therapy
• Prior IL-2-based cancer therapy
• Ongoing systemic immunosuppressive therapy
• Concurrent therapy with any other investigational agent, vaccine, or device.
• Part 3 and 4 Only: History of (non-infectious) pneumonitis/interstitial lung disease that required steroids or has current pneumonitis/interstitial lung disease
• Part 3 and 4 Only: Known additional cancer that is progressing or has required active treatment within the past 2 years. Note: Participants with basal cell carcinoma of the skin, squamous cell carcinoma of the skin, or carcinoma in situ (eg, breast carcinoma, cervical cancer in situ) that have undergone curative resection are eligible.