Study to Evaluate the Efficacy and Tolerability of Debio 1562 in Combination With Rituximab in Participants With Relapsed and/or Refractory DLBCL and Other Forms of NHL

Inclusion Criteria:

* For Part 1 of the study, participants must have histopathologically confirmed diagnosis of R/R, DLBCL, FL, MZL/MALT, MCL, or other Sponsor approved NHL subtypes according to the World Health Organization (WHO) classification 2008 for which standard measures do not exist or are no longer effective.
* For Part 2 and Part 3 of the study, participants must have histopathologically and clinically confirmed diagnosis of relapsed DLBCL. Participants will be considered to have a relapsed disease if they showed a duration of response of at least 24 weeks after their first line of therapy. The following participants with relapsed DLBCL will be enrolled:

  1. Participants who received only one line of previous therapy and achieved either complete response (CR) or partial response (PR) for at least 24 weeks (from the last day of the last cycle) after their first line of therapy, but are not eligible for high dose chemotherapy with autologous stem cell transplantation (HD-ASCT)
  2. Participants who received more than one line of previous therapy (including HD-ASCT), and have achieved a duration of response (CR or PR) of at least 8 weeks (from the last day of the last cycle) after their last line of therapy
* Participants must have evaluable or measurable disease in accordance with the International Working Group Guidelines for Lymphoma.
* Participants must have received at least one but no more than six prior treatment regimens. Prior treatment with an anti-cluster of differentiation 20 (anti-CD20) agent, either alone or in combination, is allowed.
* Participants must have Eastern Cooperative Oncology Group (ECOG) Performance Status 0 - 2.
* Participants who are Hepatitis B surface antigen positive (HBsAg+) (must be polymerase chain reaction (PCR) negative) who are taking antivirals, are allowed to enroll.

Exclusion Criteria:

* Participants with a diagnosis of chronic lymphocytic leukemia (CLL) or small lymphocytic lymphoma (SLL).
* For Part 2 and Part 3 of the study, participants with primary refractory DLBCL (defined as progression of disease within 24 weeks after first line of treatment).
* For Part 2 and Part 3 of the study, participants that are eligible to undergo first time HD-ASCT.
* For Part 2 and Part 3 of the study, participants with R/R FL, MZL/MALT, MCL, or any other NHL subtypes according to the WHO classification.
* Participants with active hepatitis A, B or C infection.
* Women who are pregnant or breast feeding.
* Participants who have received prior therapy with other anti-CD37-targeting therapy.
* Participants who have known central nervous system, meningeal, or epidural disease including brain metastases.
* Participants with impaired cardiac function or clinically significant cardiac disease.
* Participants currently presenting interstitial lung disease, diffuse parenchymal lung disease, or with a past history of severe/Grade 3 parenchymal lung disorders.