Pirtobrutinib and Mosunetuzumab for the Treatment of Relapsed/Refractory Grades 1-3A Follicular Lymphoma, PROMOTE-FL Trial

Inclusion Criteria: * Ability to understand, willing, and capable of signing a written informed consent document * Age ≥ 18 years * Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1 * Histologically confirmed FL, grades 1-3a * Relapsed after or failed to respond to at least two prior lines of systemic therapy and had received prior treatment with an anti-CD20-directed therapy * Prior treatment-related adverse events (AEs) must have recovered to grade ≤ 1 with the exception of alopecia and grade 2 peripheral neuropathy * At least one bi-dimensionally measurable lesion (≥ 1.5 cm in its largest dimension for nodal lesions, or ≥ 1.0 cm in its largest dimension for extranodal lesions within 6 weeks of screening by PET/CT scans with diagnostic computed tomography \[CT\] scan. PET/magnetic resonance imaging \[MRI\] scans may be allowed only if they are approved by the principal investigator \[PI\]) * Aspartate aminotransferase and alanine aminotransferase ≤ 3 x the upper limit of normal (ULN) * Total bilirubin ≤ 1.5 x ULN; or total bilirubin ≤ 3 x ULN in patients with documented liver involvement or in patients with a documented history of Gilbert syndrome * Platelet count ≥ 75 000/mm\^3 at any time during the screening window without requiring transfusion within 14 days prior to first dose of pirtobrutinib * Absolute neutrophil count ≥ 1000/mm\^3 in the absence of growth factor support * Total hemoglobin ≥ 10 g/dL at any time during the screening window withou…