Abstract: Introduction Patients with relapsed/refractory (R/R) diffuse large B-cell lymphoma (DLBCL) who are not eligible for autologous stem cell transplant (ASCT) have a poor prognosis. Tafasitamab (MOR208) is an Fc-enhanced, humanized, monoclonal antibody that targets CD19, which is broadly expressed across B-cell malignancies, including DLBCL. Lenalidomide (LEN) is an immunomodulatory drug with antiproliferative and antiangiogenic effects. Combined tafasitamab + LEN has shown enhanced activity in in vitro and in vivo lymphoma models. L-MIND (NCT02399085) is an ongoing, open-label, single-arm, Phase II study of tafasitamab + LEN in patients with R/R DLBCL who are ineligible for ASCT. Here, we present results from prespecified patient subgroup analyses from L-MIND. Methods Patients aged ≥18 years with R/R DLBCL (1-3 prior systemic therapies, including ≥1 CD20-targeting regimen) with an Eastern Cooperative Oncology Group performance status 0-2, and who were ineligible for ASCT were enrolled. Patients received 28-day cycles of tafasitamab (12 mg/kg intravenously), once weekly during Cycles 1-3 with a loading dose on Cycle 1 Day 4, then every 2 weeks during Cycles 4-12. LEN (25 mg orally) was administered on Days 1-21 of Cycles 1-12. After Cycle 12, progression-free patients received tafasitamab every 2 weeks until disease progression. The primary endpoint is objective response rate (ORR; partial response [PR] + complete response [CR] ), assessed centrally by an independent review committee (IRC) per International Working Group criteria 2007, incorporating PET-based imaging. Secondary endpoints include ORR (investigator-assessed), duration of response (DOR), progression-free survival (PFS), overall survival (OS), safety and biomarker analyses. Results Of 81 patients enrolled, 80 patients received tafasitamab + LEN and were included in the full analysis set (FAS) for efficacy (data cut-off 30 Nov 2018). Median follow-up was 17.3 months. In the FAS, ORR was 60.0% (95% confidence interval [CI]: 48.4-70.8) (Figure 1A). The CR rate was 42.5% (n=34/80), of which 88.2% (n=30/34) were PET-confirmed. Median time to response (PR or CR) was 2.0 months and median time to CR was 7.1 months. Median DOR was 21.7 months (95% CI: 21.7-not reached [NR] ); median PFS was 12.1 months (95% CI: 5.7-NR); and median OS was NR (95% CI: 18.3-NR) with a median follow-up of 19.6 months. The 12-month DOR and OS rates were 71.6% (95% CI: 55.1-82.9) (Figure 1B) and 73.7% (95% CI: 62.2-82.2) (Figure 1C), respectively. In the subgroup analysis, patients with CR as best objective response (BOR) had better outcomes than those with PR: median DOR, NR (95% CI: 21.7-NR) vs 4.4 months (95% CI: 2.0-9.1); 12-month DOR rate, 93.2% (95% CI: 75.4-98.3) vs 14.4% (95% CI: 1.1-43.7); and 12-month OS rate, 97.1% vs 76.9%. Patients with one prior line of therapy had a trend for better outcomes than those with ≥2 prior lines: ORR, 70.0% vs 50.0%; and 12-month OS rate, 86.9% vs 60.1%. However, the 12-month DOR rate was similar regardless of the number of prior lines (one prior line: 70.5% [95% CI: 47.2-85.0] vs ≥2 prior lines: 72.7% [95% CI: 46.3-87.6] ). For patients who were refractory to primary therapy or their last line of therapy, similar ORRs were observed to non-refractory patients (60.0% vs 60.0%); 12-month DOR was similar regardless of refractory status to last therapy; and 12-month OS rates were higher in non-refractory patients (Figure 1C). As expected, patients with a low/low-intermediate International Prognostic Index (IPI) score had better outcomes than those with an intermediate-high/high score: ORR, 70.0% vs 50.0%; 12-month DOR rate, 86.5% vs 50.4%; and 12-month OS rate, 87.0% vs 59.9%. Based on Hans algorithm, encouraging outcomes were reported in patients with germinal center B-cell (GCB) DLBCL (n=37), and outcomes were even better in those with non-GCB DLBCL (n=21): ORR, 48.6% vs 71.4%; median DOR, NR vs 21.7 months; 12-month DOR rate, 53.5% vs 83.1%; and 12-month OS rate, 65.4% vs 84.2%. Conclusions Tafasitamab + LEN combination followed by tafasitamab monotherapy shows encouraging activity with durable responses in ASCT-ineligible patients with R/R DLBCL. L-MIND includes a substantial number of poor prognosis patient subgroups. While the influence of these risk factors is evident, the clinical activity of tafasitamab + LEN in these difficult-to-treat patients is promising, particularly in those who were refractory to prior therapies. Disclosures Duell: Regeneron Pharmaceuticals, Inc.: Research Funding. Maddocks:Pharmacyclics: Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Membership on an entity's Board of Directors or advisory committees; Teva: Membership on an entity's Board of Directors or advisory committees; Novartis: Research Funding; Merck: Research Funding; BMS: Research Funding. González-Barca:Janssen: Consultancy, Honoraria; Kiowa: Consultancy; Celtrion: Consultancy; Celgene: Consultancy; AbbVie: Consultancy, Honoraria; Roche: Consultancy, Honoraria; Takeda: Honoraria. Jurczak:TG Therapeutics: Research Funding; Roche: Research Funding; Takeda: Research Funding; Servier: Research Funding; Celtrion: Research Funding; Novo Nordisk: Research Funding; Incyte: Research Funding; Bayer: Research Funding; Loxo: Membership on an entity's Board of Directors or advisory committees, Research Funding; AstraZeneca: Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Membership on an entity's Board of Directors or advisory committees, Research Funding; Gilead: Research Funding; Sandoz: Membership on an entity's Board of Directors or advisory committees, Research Funding; MorphoSys: Research Funding. Liberati:Incyte: Consultancy; Janssen: Honoraria; Servier: Honoraria, Membership on an entity's Board of Directors or advisory committees; AbbVie: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Honoraria; Takeda: Membership on an entity's Board of Directors or advisory committees; Amgen: Membership on an entity's Board of Directors or advisory committees; Bristol & Mayer: Honoraria. de Vos:Bayer: Consultancy; Verastem: Consultancy; Portola Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees. Nagy:Janssen: Membership on an entity's Board of Directors or advisory committees; Abbvie: Membership on an entity's Board of Directors or advisory committees; Roche: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Takeda: Membership on an entity's Board of Directors or advisory committees. Gaidano:AbbVie: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Sunesys: Consultancy, Honoraria; Astra-Zeneca: Consultancy, Honoraria; Janssen: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Abrisqueta:Celgene: Consultancy, Honoraria; Janssen: Consultancy, Honoraria, Other: Travel, Accommodations, expenses, Speakers Bureau; Roche: Consultancy, Honoraria, Other: Travel, Accommodations, expenses, Speakers Bureau; Abbvie: Consultancy, Honoraria, Other: Travel, Accommodations, expenses, Speakers Bureau. André:Takeda: Membership on an entity's Board of Directors or advisory committees; Bristol-Myers-Squibb: Membership on an entity's Board of Directors or advisory committees; Karyopharm: Membership on an entity's Board of Directors or advisory committees; Gilead: Membership on an entity's Board of Directors or advisory committees, Other: Travel grants; Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding; Seattle Genetics: Membership on an entity's Board of Directors or advisory committees; Abbvie: Membership on an entity's Board of Directors or advisory committees; Roche: Other: Travel grants, Research Funding; Amgen: Other: Travel grants, Research Funding; Johnson & Johnson: Research Funding; Takeda Millenium: Research Funding; Chugai: Research Funding; Celgene: Other: Travel grants, Research Funding. Dreyling:Celgene: Other: Scientific advisory board, Research Funding, Speakers Bureau; Gilead: Other: Scientific advisory board, Speakers Bureau; Janssen: Other: Scientific advisory board, Research Funding, Speakers Bureau; Mundipharma: Other: Scientific advisory board, Research Funding; Novartis: Other: Scientific advisory board; Roche: Other: Scientific advisory board, Research Funding, Speakers Bureau; Sandoz: Other: Scientific advisory board; Acerta: Other: Scientific advisory board; Bayer: Other: Scientific advisory board, Speakers Bureau. Menne:Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Kite/Gilead: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel grant, Research Funding, Speakers Bureau; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel grant, Research Funding, Speakers Bureau; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel grant; Daiichi Sankyo: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel grant, Research Funding, Speakers Bureau; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Bayer: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel grant, Research Funding, Speakers Bureau; Jazz: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel grant, Research Funding, Speakers Bureau; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Astra Zeneca: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Kyowa Kirin: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel grant, Research Funding, Speakers Bureau. Dirnberger-Hertweck:MorphoSys: Employment. Weirather:MorphoSys: Employment. Ambarkhane:MorphoSys: Employment. Salles:Merck: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Amgen: Honoraria, Other: Educational events; Takeda: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Educational events; Roche, Janssen, Gilead, Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Educational events; Epizyme: Consultancy, Honoraria; Novartis, Servier, AbbVie, Karyopharm, Kite, MorphoSys: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Educational events; Autolus: Consultancy, Membership on an entity's Board of Directors or advisory committees; BMS: Honoraria.