∙ Participants are eligible to be included in the study only if all the following criteria apply.

• Subject has voluntarily agreed to participate by giving written informed consent in accordance with ICH/GCP guidelines and applicable local regulations.

• Subject has a histologically confirmed diagnosis of one of the following unresectable locally advanced or metastatic malignancies: melanoma, non-small cell lung cancer (squamous, adeno, or adeno-squamous), urothelial cancer, squamous cell carcinoma of the head and neck, squamous cell cervical cancer, gastric or gastro-esophageal junction adenocarcinoma, squamous cell carcinoma of the anal canal, squamous cell carcinoma of the skin, renal cell cancer, Hodgkin's lymphoma, and microsatellite instability high (MSI-H) or mismatch repair deficient (MMRD) solid tumors excluding CNS malignancies. MSI and MMRD testing results as per institution is acceptable.

‣ Head and neck cancers: Subjects must have primary tumor locations in the oropharynx, oral cavity, hypopharynx, or larynx. Primary tumor sites of nasopharynx, maxillary sinus, paranasal, and unknown primary are excluded.

⁃ Non-small cell lung cancers: Subjects with a known EGFR sensitizing (activating) mutation or an ALK fusion are excluded.

• Subject must have received, been intolerant to, or is ineligible for standard therapy (per local guidelines and approvals) or have a malignancy for which there is no approved therapy considered standard of care.

• Age 18 years and older.

• Has an Eastern Cooperative Oncology Group Performance Status (ECOG PS) of 0 or 1.

• Has measurable disease by iRECIST (solid tumors) or RECIL 2017 (lymphoma). Refer to Appendix Sections 16.6 and 16.7 for details on criteria of measurable disease.

• Has life expectancy of greater than 12 weeks.

• Laboratory values must meet the following criteria. Laboratory parameter Threshold value

‣ Absolute lymphocyte count (ALC) ≥ 0.8 x 109/liter (L)

⁃ Absolute neutrophil count (ANC) ≥ 1.5 x 109/L without growth factor support

⁃ Platelet count ≥ 50 x 109/L

• Laboratory parameter Threshold value

⁃ Hemoglobin (Hgb) \> 9.0 g/dL with no blood transfusions for at least 5 days prior to D1 of investigational product (IP; SL-279252)

⁃ Creatinine clearance (CrCl) ≥ 30 milliliter (mL)/min (modified Cockcroft-Gault)

⁃ ALT/AST ≤ 3 x ULN

⁃ Total bilirubin ≤ 1.5 x ULN; subjects with isolated indirect hyperbilirubinemia are permitted if direct bilirubin ratio is \<35% and total bilirubin is ≤ 3.0 x ULN

⁃ Left ventricular ejection fraction (LVEF) by echocardiogram (ECHO) ≥ lower limit of normal (LLN) per institutional threshold. If LLN is not defined for a given institution, then ejection fraction must be ≥50 %.

• Females of child bearing potential (FCBP) must have a negative serum or urine pregnancy test within 72 hours of D1 of IP. NOTE: FCBP unless they are surgically sterile (i.e., have undergone a complete hysterectomy, bilateral tubal ligation/occlusion, bilateral oophorectomy or bilateral salpingectomy), have a congenital or acquired condition that prevents childbearing or are naturally postmenopausal for at least 12 consecutive months (see Appendix Section 16.2 for additional details). Documentation of postmenopausal status must be provided. FCBP should use an acceptable method of contraception (see Appendix Section 16.2) to avoid pregnancy during treatment and for 30 days (which exceeds 5 half-lives) after the last dose of IP. FCBP must start using acceptable contraception at least 14 days prior to D1 of IP.

⁃ Male subjects with female partners must have azoospermia from a prior vasectomy or underlying medical condition or agree to use an acceptable method of contraception during treatment and for 30 days (which exceeds 5 half-lives) after last dose of SL-279252 (see Appendix Section 16.2). Male subjects of reproductive potential must start using acceptable contraception at least 14 days prior to D1 of treatment with SL-279252 as per Appendix Section 16.2.

⁃ All AEs resulting from prior anti-cancer immunotherapy have resolved (NOTE: exceptions include alopecia, vitiligo, and endocrinopathies adequately treated with hormone replacement).

⁃ • Subjects that were discontinued from prior PD-1/L1 therapy due to immune-related adverse events are not eligible

⁃ Recovery from toxicities from prior anti-cancer treatments including surgery, radiotherapy, chemotherapy or any other anti-cancer therapy to baseline or ≤ Grade 1. (NOTE: Low-grade toxicities (e.g., alopecia, ≤ Grade 2 lymphopenia, ≤ Grade 2 hypomagnesemia, ≤ Grade 2 neuropathy) may be allowed at the discretion of the investigator if considered clinically insignificant. Please consult the Sponsor Medical Monitor to discuss these cases).