A Trial to Learn if Odronextamab Combined With Chemotherapy is Safe and Well-Tolerated and How Well it Works Compared to Rituximab Combined With Chemotherapy for Adult Participants With Follicular Lymphoma

This study is researching an experimental drug called odronextamab, referred to as study drug. The study is focused on participants with previously untreated follicular lymphoma. Follicular lymphoma is a type of non-Hodgkin lymphoma or NHL. Participants with follicular lymphoma that has come back after treatment (called "relapsed") or did not respond to treatment (called "refractory") are eligible to take part only in Part 1A of the study.

This study is made up of 3 parts: Part 1A (non-randomized), Part 1B and Part 2 (randomized - controlled).

The aim of Part 1A and Part 1B of the study is to see how safe and tolerable the study drug in combination with chemotherapy is and to determine the dose and schedule of the study drug to be combined with chemotherapy to be used in Part 2 of the study.

The aim of Part 2 of the study is to assess how effective the combination of the study drug with chemotherapy is in comparison with the combination of rituximab and chemotherapy (the current standard-of-care for NHL). Standard-of-care means the usual medication expected and used when receiving treatment for a condition.

The study is looking at several other research questions, including:

* What side effects may happen from taking the study drug
* How much study drug is in the blood at different times
* Whether the body makes antibodies against the study drug (which could make the study drug less effective or could lead to side effects)
* The impact from the study drug on quality-of-life and ability to complete routine daily activities


Eligibility Criteria:
Key Inclusion Criteria:

1. Have diagnosis of cluster of differentiation 20 positive (CD20+) FL grade 1-3a, stage II bulky or stage III / IV

   1. For Part 1A: previously untreated participants who have Follicular Lymphoma International Prognostic Index (FLIPI)-1 score of 3 to 5, or R/R FL
   2. For Part 1B: previously untreated participants who have FLIPI-1 score of 3 to 5
   3. For Part 2: previously untreated participants who have FLIPI-1 score of 0 to 5
2. Have measurable disease on cross sectional imaging documented by diagnostic computed tomography \[CT\], or magnetic resonance imaging \[MRI\] imaging, as described in the protocol
3. Eastern Cooperative Oncology Group (ECOG) performance status of 0-2
4. Adequate bone marrow and hepatic function.

Key Exclusion Criteria:

1. Participants with central nervous system lymphoma or leptomeningeal lymphoma
2. Participants with histological evidence of transformation to a high-grade or diffuse large B-cell lymphoma
3. Participants with Waldenström macroglobulinemia (WM, lymphoplasmacytic lymphoma), grade 3b follicular lymphoma, chronic lymphocytic leukemia or small lymphocytic lymphoma
4. Recent major surgery and history or organ transplantation
5. A malignancy other than NHL unless the participant is adequately and definitively treated and any other significant active disease or medical condition that could interfere with the conduct of the study or put the participant at significant risk, as described in the protocol.

Note: Other protocol-defined Inclusion/Exclusion criteria apply