For a patient with relapsed indolent follicular lymphoma (grade 1‑3a) who progressed on rituximab‑lenalidomide (R2), is epcoritamab combined with rituximab the most appropriate next therapy?

No, epcoritamab + rituximab is NOT appropriate after progression on R2 (rituximab-lenalidomide)

Based on the most recent and highest-quality evidence, epcoritamab should be combined with BOTH lenalidomide AND rituximab (epcoritamab + R2), not just rituximab alone, for patients who have progressed on R2. The pivotal EPCORE FL-1 trial specifically evaluated epcoritamab + R2 versus R2 alone in relapsed/refractory follicular lymphoma, demonstrating superior outcomes with the triple combination 1.

Key Evidence Supporting Epcoritamab + R2 (Not Epcoritamab + Rituximab Alone)

The 2026 EPCORE FL-1 phase 3 trial enrolled 488 patients with relapsed/refractory follicular lymphoma after at least one prior line of chemoimmunotherapy 1. The trial compared epcoritamab + lenalidomide + rituximab versus lenalidomide + rituximab alone—NOT epcoritamab + rituximab without lenalidomide.

Efficacy Results:

• Overall response rate: 95% with epcoritamab + R2 versus 79% with R2 alone (p<0.0001)
• Progression-free survival: Hazard ratio 0.21 (95% CI 0.14-0.31, p<0.0001), representing a 79% reduction in risk of progression or death
• 16-month PFS: 85.5% versus 40.2% 1

This positions epcoritamab + R2 as a new standard of care for second-line or subsequent treatment of follicular lymphoma 1.

Why This Matters for Your Patient

The question implies using epcoritamab + rituximab after R2 failure, which would mean re-challenging with rituximab but omitting lenalidomide. This approach lacks evidence support. The EPCORE FL-1 trial specifically included patients who had received prior therapy (including those who may have had prior lenalidomide exposure), and the winning regimen was the triple combination.

Current Guideline Framework:

The 2025 NCCN Guidelines now include epcoritamab as an approved therapy for relapsed/refractory FL after ≥2 prior systemic therapies 2. However, the guidelines reference epcoritamab as a CD3 × CD20 bispecific antibody option alongside other third-line therapies like CAR T-cell therapy and zanubrutinib + obinutuzumab 2.

The 2021 ESMO guidelines (predating epcoritamab approval) recommend for relapsed FL:

• In rituximab-refractory cases or remissions <6 months: obinutuzumab-bendamustine plus obinutuzumab maintenance 3
• For later relapses: non-chemotherapy approaches including lenalidomide + rituximab 3

Clinical Decision Algorithm

For a patient progressing on R2:

1. Confirm CD20 positivity with re-biopsy (strongly recommended at relapse per ESMO guidelines 3)

2. Assess timing of progression:

   • If progression occurred during or shortly after R2 (suggesting R2-refractory disease), this patient needs a different mechanism of action
   • The EPCORE FL-1 trial included patients after ≥1 prior line, meaning some had R2 exposure 1

3. Consider epcoritamab + R2 (triple therapy) as the evidence-based option:

   • This is the regimen proven in the pivotal trial 1
   • Administered as: epcoritamab weekly in cycles 1-3, then every 4 weeks in cycles 4-12; lenalidomide days 1-21 of cycles 1-12; rituximab weekly in cycle 1, monthly in cycles 2-5 1

4. Alternative third-line options if epcoritamab + R2 is not feasible:

   • CD19-directed CAR T-cell therapy (axi-cel, tisa-cel, liso-cel) 2
   • Epcoritamab monotherapy (82% ORR, 62.5% CR rate in third-line setting) 4
   • Mosunetuzumab (another CD3 × CD20 bispecific) 2
   • Zanubrutinib + obinutuzumab 2

Safety Considerations

Epcoritamab + R2 had manageable toxicity 1:

• Grade ≥3 adverse events: 90% (versus 68% with R2 alone)
• Cytokine release syndrome: predominantly grade 1 (21%) and grade 2 (5%), all resolved
• No new safety signals beyond known profiles of individual agents

Critical pitfall: The step-up dosing for epcoritamab (0.16 mg priming → 0.8 mg intermediate → 48 mg full doses) is essential to mitigate CRS risk 1, 4.

Why Not Epcoritamab + Rituximab Alone?

There is no published evidence supporting epcoritamab + rituximab (without lenalidomide) in this setting. The monotherapy epcoritamab data (EPCORE NHL-1) showed 82% ORR in third-line FL 4, but this was single-agent therapy, not epcoritamab + rituximab doublet.

The synergy demonstrated in EPCORE FL-1 was specifically with the triple combination 1. Removing lenalidomide from this regimen would be:

• Unsupported by evidence
• Potentially less effective than proven alternatives
• Not aligned with the FDA approval or guideline recommendations

Bottom Line

Use epcoritamab + lenalidomide + rituximab (the full triple combination) for patients progressing on R2, not epcoritamab + rituximab alone. If the triple combination is not feasible, consider epcoritamab monotherapy or other third-line options (CAR T, other bispecifics, or zanubrutinib-based therapy) rather than an unproven doublet regimen 2, 1, 4.