A Clinical Trial in Adults With Non-Hodgkin Lymphoma (NHL), With a Particular Emphasis on Cutaneous T Cell Lymphoma (CTCL), Testing the Safety and Activity of a Novel Drug to Inhibit a Protein Called Tumor Necrosis Factor Receptor 2 That Drives Both Lymphoma Growth and Escape of the Immune System

Key Inclusion Criteria: * Histologically confirmed relapsed or refractory B cell NHL (DLBCL, MCL, MZL), PTCL or CTCL (MF or SS subtype) as per 2017 World Health Organization classification after at least 2 prior lines of systemic therapy and have received, or are not eligible for, approved or available treatments expected to provide benefit. CTCL patients should be Stage ≥1B through 4 and Stage 1A (see Appendix 1) with plaque disease without treatment options, in which case the patient should be discussed with the sponsor after submitting documentation of disease stage and treatment history. Patients with indolent lymphoid malignancies (CTCL, MZL) must need new treatment regimen in the opinion of the treating Investigator. * Age ≥18 years. * Life expectancy ≥3 months. * Eastern Cooperative Oncology Group (ECOG) Performance Status of 0 or 1. Key Exclusion Criteria: * Patients with prior exposure (up to 12 months) to PD-1/PD-L1 therapies. * Known hypersensitivity to any excipients that are used in the BITR2101 formulation as noted in Investigator Brochure. * Autoimmune diseases that have been sufficiently active to require medications in the 3 months before screening, except autoimmune endocrinopathies, such as hypothyroidism, that are stable with hormone-replacement therapy. Including inflammatory diseases such as arthritis, colitis, liver fibrosis, cirrhosis, interstitial fibrosis or chronic obstructive pulmonary disease (COPD). The SRC may allow patients with well controlled arthritis or COPD in the expansion cohort if there is no indication of inflammatory disease flare and no blood cytokine evidence of a systemic inflammatory response in the 3 months prior to enrollment. * Serious illness or concomitant non-oncological disease considered by the investigator to be incompatible with participating in the protocol. * History or evidence of clinically significant cardiovascular disease. * Severe dyspnea, pulmonary dysfunction, or need for continuous supportive oxygen inhalation. * Concurrent enrollment in another clinical study, unless it is an observational (non-interventional) clinical study for the duration of this study or the FU period of an interventional study. * Prior or current anticancer therapy, including chemotherapy, hormonal therapy, or radiotherapy within 4 weeks of the first BITR2101 administration. * Continuous corticosteroid use exceeding 10 mg/day prednisone or equivalent. Other protocol defined Inclusion/Exclusion criteria may apply