The purpose of this study is to evaluate safety and tolerability and to determine the maximum tolerated dose (MTD) or maximum administered dose (MAD) and/or recommended dose (RD) of SGR-1505.

This is a study of SGR-1505, an oral inhibitor of MALT1, in subjects with relapsed/refractory (R/R) B-cell lymphomas to evaluate the safety, pharmacokinetics (PK), pharmacodynamics (PD), maximum tolerated dose (MTD) or maximum administered dose (MAD) and/or recommended dose (RD) of SGR-1505. Exploratory cohorts will evaluate additional PK, PD, preliminary anti-tumor activity, and safety to establish the SGR-1505 RD. A planned amendment will evaluate SGR-1505 in combination with other anti-cancer agents, such as BTK and BCL-2 inhibitors, in patients with specific B-cell malignancies.

Inclusion Criteria:

• Subject must have a history of histologically or cytologically confirmed mature B-cell malignancy.
• Subject must have measurable or detectable disease according to the applicable disease-specific classification system and meet criteria for initiation of treatment.
• Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1.
• Life expectancy ≥ 12 weeks.

Exclusion Criteria:

• The subject is in need of immediate cytoreductive therapy (unless the patient has no remaining treatment choice with potential benefit).
• Subject has previous invasive malignancy in the last 2 years.
• Subject has a known allergy to SGR-1505 or excipients of SGR-1505.
• Subject has symptomatic or active CNS involvement of disease.
• Any other diseases, metabolic dysfunction, physical examination finding, or clinical laboratory finding that would place the participant at increased risk to the use of an investigational drug.