Abstract: Introduction: Patients (pts) with CLL may be at particular risk of severe COVID-19 given advanced age and immune dysregulation. Two large series with limited follow-up have reported outcomes for pts with CLL and COVID-19 (Scarfò, et al. Leukemia 2020; Mato, et al. Blood 2020). To provide maximal clarity on outcomes for pts with CLL and COVID-19, we partnered in a worldwide effort to describe the clinical experience and validate predictors of survival, including potential treatment effects. Methods: This international collaboration represents a partnership between investigators at 141 centers. Data are presented in two cohorts. Cohort 1 (Co1) includes pts captured through efforts by European Research Initiative on CLL (ERIC), Italian CAMPUS CLL Program, and Grupo Español de Leucemia Linfática Crónica. The validation cohort, Cohort 2 (Co2), includes pts from US (66%), UK (23%), EU (7%), and other countries (4%). There is no overlap in cases between cohorts. CLL pts were included if COVID-19 was diagnosed by PCR detection of SARS-CoV-2 and they required inpatient hospitalization. Data were collected retrospectively 2/2020 - 5/2020 using standardized case report forms. Baseline characteristics, preexisting comorbidities (including cumulative illness rating scale (CIRS) score ≥6 vs. & lt;6), CLL treatment history, details regarding COVID-19 course, management, and therapy, and vital status were collected. The primary endpoint of this study was to estimate the case fatality rate (CFR), defined as the proportion of pts who died among all pts hospitalized with COVID-19. Chi-squared test was used to compare frequencies; univariable and multivariable analyses utilized Cox regression. Predictors of inferior OS in both Co1 and Co2 were included in multivariable analyses. Kaplan-Meier method was used to estimate overall survival (OS) from time of COVID-19 diagnosis (dx). Results: 411 hospitalized, COVID-19 positive CLL pts were analyzed (Co1 n=281, Co2 n=130). Table 1 describes baseline characteristics. At COVID-19 dx, median age was 72 in Co1 (range 37-94) and 68 in Co2 (range 41-98); 31% (Co1) and 45% (Co2) had CIRS ≥6. In Co1, 48% were treatment-naïve and 26% were receiving CLL-directed therapy at COVID-19 dx (66% BTKi ± anti-CD20, 19% Venetoclax ± anti-CD20, 9.6% chemo/chemoimmunotherapy (CIT), 1.4% PI3Ki, 4% other). In Co2, 36% were never treated and 49% were receiving CLL-directed therapy (65% BTKi ± anti-CD20, 19% Venetoclax ± anti-CD20, 9.4% multi-novel agent combinations, 1.6% CIT, 1.6% PI3Ki, 1.6% anti-CD20 monotherapy, 1.6% other). Most pts receiving CLL-directed therapy had it held at COVID-19 diagnosis (93% in Co1 and 81% in Co2). Frequency of most COVID-19 symptoms/laboratory abnormalities were similar in the two cohorts including fever (88% in both), lymphocytosis (ALC ≥30 x 109/L; 27% vs. 21%), and lymphocytopenia (ALC & lt; 1.0 x 109/L; 18% vs. 28%), while others varied between Co1 and Co2 (p & lt;0.0001), including cough (61% vs. 93%), dyspnea (60% vs. 84%), fatigue (13% vs. 77%). Median follow-up was 24 days (range 2-86) in Co1 and 17 days (1-43) in Co2. CFRs were similar in Co1 and Co2, 30% and 34% (p=0.45). 54% and 43% were discharged while 16% and 23% remained admitted at last follow-up in Co1 and Co2, respectively. The proportion of pts requiring supplemental oxygen was similar (89% vs. 92%) while rate of ICU admission was higher in Co2 (20% vs. 48%, p & lt;0.0001). Figure 1 depicts OS in each cohort. Univariable analyses demonstrated that age and CIRS ≥6 significantly predicted inferior OS in both cohorts, while only age remained an independent predictor of inferior OS in multivariable analyses (Table 2). Prior treatment for CLL (vs. observation) predicted inferior OS in Co1 but not Co2. Conclusions : In the largest cancer dx-specific cohort reported, pts with CLL hospitalized for COVID-19 had a CFR of 30-34%. Advanced patient age at COVID-19 diagnosis was an independent predictor of OS in two large cohorts. This CFR will serve as a benchmark for mortality for future outcomes studies, including therapeutic interventions for COVID-19 in this population. The effect of CLL treatment on OS was inconsistent across cohorts; COVID-19 may be severe regardless of treatment status. While there were no significant differences in distribution of current lines of therapy between cohorts, prior chemo exposure was more common in Co1 vs. Co2, which may account for difference in OS. Extended follow-up will be presented. Disclosures Roeker: American Society of Hematology: Research Funding; Abbott Laboratories: Other: spouse with minority ownership interest ; AbbVie: Other: spouse with minority ownership interest . Scarfo:Janssen: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Abbvie: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; AstraZeneca: Honoraria; Gilead: Membership on an entity's Board of Directors or advisory committees. Abrisqueta:Celgene: Consultancy, Honoraria; Janssen: Consultancy, Honoraria, Speakers Bureau; Roche: Consultancy, Honoraria, Speakers Bureau; AbbVie: Consultancy, Honoraria, Speakers Bureau. Eyre:AbbVie: Consultancy, Honoraria, Other: travel support; Gilead: Consultancy, Honoraria, Other: travel support; Janssen: Consultancy, Honoraria, Other: travel support; KITE, AZ, Loxo Oncology at Lilly: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Muntañola Prat:Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: travel grants; participated in advisory boards; Abbvie: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: travel grants; participated in advisory boards; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: travel grants; participated in advisory boards. Villacampa:AstraZeneca: Other: advisory role; Merck Sharp & Dohme: Honoraria. Leslie:AstraZeneca: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Bayer: Consultancy, Membership on an entity's Board of Directors or advisory committees; ADC therapeutics: Consultancy, Membership on an entity's Board of Directors or advisory committees; AbbVie: Consultancy, Membership on an entity's Board of Directors or advisory committees; BeiGene: Speakers Bureau; KitePharma: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Celgene/BMS: Speakers Bureau; Seattle Genetics: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Pharmacyclics/Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Epizyme: Speakers Bureau; Karyopharm: Speakers Bureau; TG Therapeutics: Consultancy, Membership on an entity's Board of Directors or advisory committees. Allan:Acerta, Genentech, Abbvie, Sunesis, Ascentage, Pharmacyclics, Janssen, AstraZeneca, BeiGene: Consultancy; Celgene, Genentech, Janssen, TG Therapeutics: Research Funding; Abbvie, Janssen, AstraZeneca, Pharmacyclics: Honoraria. Furman:Incyte: Consultancy; Genentech: Consultancy; Sunesis: Consultancy; Pharmacyclics: Consultancy; Loxo Oncology: Consultancy; Oncotarget: Consultancy; Janssen: Consultancy, Speakers Bureau; TG Therapeutics: Consultancy, Research Funding; Abbvie: Consultancy; Beigene: Consultancy; AstraZeneca: Consultancy, Research Funding; Acerta: Consultancy; Verastem: Consultancy. Pagel:BeiGene, Astrazeneca, Loxo Oncology, Gilead: Consultancy. Hernandez-Rivas:Gilead: Membership on an entity's Board of Directors or advisory committees; Celgene/BMS: Membership on an entity's Board of Directors or advisory committees; 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; AstraZeneca: Membership on an entity's Board of Directors or advisory committees; Rovi: Membership on an entity's Board of Directors or advisory committees. Patel:Genentech: Consultancy, Speakers Bureau; Adaptive Biotechnologies: Consultancy; Janssen: Consultancy, Speakers Bureau; Celgene/BMS: Consultancy, Membership on an entity's Board of Directors or advisory committees; BeiGene: Consultancy; Kite: Consultancy; Pharmacyclics: Consultancy, Speakers Bureau; AstraZeneca: Consultancy, Research Funding, Speakers Bureau. Motta:Roche: Honoraria; Janssen: Honoraria. Lamanna:AbbVie: Membership on an entity's Board of Directors or advisory committees, Research Funding; Pharmacyclics: Membership on an entity's Board of Directors or advisory committees; Gilead: 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; Genentech: Research Funding; Verastem: Research Funding; Bei-Gene: Research Funding; TG Therapeutics: Research Funding; Acerta: Research Funding; Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; Roche-Genentech: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees. Vitale:Janssen: Honoraria. Kamdar:Roche: Research Funding. Österborg:BeiGene: Research Funding; Kancera: Current equity holder in publicly-traded company, Research Funding; Sanofi: Consultancy; Karolinska Univeristy Hospital, Stockholm, Sweden: Current Employment. Hanson:Janssen-Cilag: Research Funding; Gilead: Research Funding; AbbVie: Honoraria. Eichhorst:ArQule: Consultancy, Honoraria, Other: travel support, Research Funding; BeiGene: Consultancy, Honoraria, Other: travel support, Research Funding; Gilead: Consultancy, Honoraria, Other: travel support, Research Funding; AstraZeneca: Consultancy, Honoraria, Other: travel support, Research Funding; Oxford Biomedica: Consultancy, Honoraria, Other: travel support, Research Funding; AbbVie: Consultancy, Honoraria, Other: travel support, Research Funding; F. Hoffmann-LaRoche: Consultancy, Honoraria, Other: travel support, Research Funding; Janssen-Cilag: Consultancy, Honoraria, Other: travel support, Research Funding; Celgene: Consultancy, Honoraria, Other: travel support, Research Funding; Novartis: Consultancy, Honoraria, Other: travel support, Research Funding. Reda:Gilead: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees; Abbvie: Membership on an entity's Board of Directors or advisory committees. Varettoni:Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: Travel/accommodations/expenses; AbbVie: Other: Travel/accommodations/expenses; Roche: Consultancy, Membership on an entity's Board of Directors or advisory committees. Marchetti:Gilead: Consultancy; Novartis: Speakers Bureau; Amgen: Speakers Bureau; AbbVie: Other: Sponsored meetings; Takeda: Other: Sponsored meetings; Pfeizer: Other: Sponsored meetings. Munir:F. Hoffmann-La Roche: Consultancy, Other: Medical writing support, furnished by Scott Battle, PhD, of Health Interactions, was funded by F. Hoffmann-La Roche Ltd, Basel, Switzerland; Alexion: Honoraria. Zabalza:Janssen: Honoraria, Other: travel grants; Roche: Other: travel grants; Novartis: Other: travel grants. Janssens:Amgen: Consultancy, Other: travel grants; speaker fees; Abbvie: Consultancy, Other: travel grants; speaker fees; Celgene: Consultancy, Other: travel grants; speaker fees; Janssen: Consultancy, Other: travel grants; speaker fees; Gilead: Consultancy, Other: travel grants; speaker fees; Novartis: Consultancy, Other: travel grants; speaker fees; Sanofi-Genzyme: Consultancy, Other: travel grants; speaker fees; Roche: Consultancy, Other: travel grants; speaker fees. Niemann:AstraZeneca: Honoraria, Research Funding; CSL Behring: Honoraria, Research Funding; Janssen: Honoraria, Research Funding; Sunesis: Honoraria, Research Funding; Abbvie: Honoraria, Research Funding; Danish Cancer Society: Honoraria, Research Funding; Novo Nordisk Foundation: Honoraria, Research Funding. Perini:Takeda: Honoraria; Janssen: Honoraria, Speakers Bureau; Abbvie: Speakers Bureau. Patten:AbbVie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Roche: Consultancy, Honoraria; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen: Consultancy, Honoraria; Gilead: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Astra Zeneca: Honoraria. Marasca:Roche: Membership on an entity's Board of Directors or advisory committees; Abbvie: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Janssen: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Shire: Honoraria. Iyengar:Janssen: Honoraria; Gilead: Honoraria. Ferrari:Abbvie: Honoraria. El-Sharkawi:Roche: Other: Conference fees; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees. Itchaki:Abbvie Inc: Consultancy, Research Funding. Ma:Novartis: Research Funding; Juno: Research Funding; Pharmacyclics, LLC, an AbbVie Company: Consultancy, Honoraria, Research Funding, Speakers Bureau; Kite: Consultancy, Honoraria; Janssen: Consultancy, Honoraria, Research Funding, Speakers Bureau; Gilead: Consultancy, Honoraria; Genentech: Consultancy, Honoraria; Bioverativ: Consultancy, Honoraria; BeiGene: Honoraria, Research Funding, Speakers Bureau; AstraZeneca: Consultancy, Honoraria, Research Funding, Speakers Bureau; AbbVie: Consultancy, Honoraria, Research Funding; TG Therapeutics: Research Funding. Van Der Spek:AMGEN: Other: Teaching activities. Seymour:Seattle Genetics: Research Funding; Merck: Research Funding; Karyopharm: Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen/Pharmacyclics: Membership on an entity's Board of Directors or advisory committees; Incyte: Research Funding; Genentech: Research Funding; Bristol-Myers Squibb: Research Funding. Rigolin:Gilead: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Janssen: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Abbvie: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Mauro:Roche: Other; Octopharma: Other; Takeda-Shire: Other; Gilead: Other; Janssen: Other; Abbvie: Other. Laurenti:Janssen: Honoraria; Gilead: Honoraria; AbbVie: Honoraria; Roche: Honoraria. Levin:Janssen: Membership on an entity's Board of Directors or advisory committees, Other: travel compensation; Abbvie: Membership on an entity's Board of Directors or advisory committees, Other: travel compensation; Roche: Membership on an entity's Board of Directors or advisory committees, Other: travel compensation. Špaček:Gilead: Honoraria; Abbvie: Honoraria; Janssen: Honoraria. Walewska:AbbVie: Other: sponsored for educational meetings, Speakers Bureau; Janssen: Other: sponsored for educational meetings, Speakers Bureau; Gilead: Speakers Bureau; Astra Zeneca: Membership on an entity's Board of Directors or advisory committees. Wiestner:Pharmacyclics LLC, an AbbVie Company; Acerta, Merck, Nurix, Verastem, and Genmab: Research Funding; National Institutes of Health: Patents & Royalties: and other intellectual property. Broom:Gilead: Other: Travel support, Speakers Bureau. Kater:Abbvie: Research Funding; Roche: Research Funding; Janssen: Research Funding; Celgene: Research Funding; Genentech: Research Funding. Ujjani:AstraZeneca: Consultancy, Honoraria, Research Funding; Abbvie: Consultancy, Honoraria, Research Funding; Verastem Oncology: Consultancy, Honoraria; Gilead/Kite: Consultancy, Research Funding; Atara: Consultancy, Honoraria; Genentech: Consultancy, Honoraria; MorphoSys: Consultancy. Vandenberghe:Celgene: Other: sponsorship to attend Lugano lymphoma meeting in 2019; Gilead: Other: travel grants, Research Funding; Abbvie: Other: travel grants, Research Funding; Janssen: Other: travel grants; Roche: Other: travel grants, Research Funding. Chong:Novartis: Membership on an entity's Board of Directors or advisory committees; Tessa: Membership on an entity's Board of Directors or advisory committees; BMS: Membership on an entity's Board of Directors or advisory committees; KITE Pharma: Membership on an entity's Board of Directors or advisory committees. Pu:Takeda Pharmaceuticals: Consultancy. Brown:Janssen, Teva: Speakers Bureau; Gilead, Loxo, Sun, Verastem: Research Funding; Abbvie, Acerta, AstraZeneca, Beigene, Invectys, Juno/Celgene, Kite, Morphosys, Novartis, Octapharma, Pharmacyclics, Sunesis, TG Therapeutics, Verastem: Consultancy. Trentin:Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Abbvie: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Octapharma: Membership on an entity's Board of Directors or advisory committees; Takeda: Membership on an entity's Board of Directors or advisory committees; Shire: Honoraria. Farina:Abbvie: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees. Sanchez:Abbvie: Other: travel grants; Amgem: Other: travel grants; Janssen: Other: travel grants; Celgene: Other: travel grants; Roche: Other: travel grants. Shadman:Abbvie, Genentech, Astra Zeneca, Sound Biologics , Pharmacyclics, Verastem, ADC therapeutics, Beigene, Cellectar, BMS, Morphosys and Atara Biotherapeutics: Consultancy; Mustang Bio, Celgene, Pharmacyclics, Gilead, Genentech, Abbvie, TG therapeutics, Beigene, Astra Zeneca, Sunesis, Beigene: Research Funding. Foglietta:Janssen: Honoraria; Gilead: Honoraria. Jaksic:Roche: Honoraria; Janssen: Honoraria; Abbvie: Honoraria. Sportoletti:AbbVie: Honoraria; Janssen: Honoraria. Barr:Morphosys: Consultancy; Gilead: Consultancy; AstraZeneca: Consultancy, Research Funding; Verastem: Consultancy; Seattle Genetics: Consultancy; TG therapeutics: Consultancy, Research Funding; Abbvie/Pharmacyclics: Consultancy, Research Funding; Celgene: Consultancy; Merck: Consultancy; Genentech: Consultancy; Janssen: Consultancy. Ruchlemer:Abbvie Inc: Consultancy, Research Funding. Kersting:Celgene: Other: travel grant; Janssen: Research Funding; Abbvie: Research Funding. Huntington:Pharmacyclics: Honoraria; AbbVie: Consultancy; Novartis: Consultancy; Genentech: Consultancy; DTRM: Research Funding; Celgene: Consultancy, Research Funding; Bayer: Consultancy, Honoraria; Astrazeneca: Honoraria; TG Therapeutics: Research Funding. Herishanu:Roche: Honoraria; Sanofi: Honoraria; Medison: Honoraria; Janssen: Honoraria; Abbvie: Honoraria; AstraZeneca: Honoraria. Jacobs:TG Therapeutics, Inc.: Research Funding; Astra Zeneca: Consultancy, Speakers Bureau; AbbVie: Consultancy, Speakers Bureau; Pharmacyclics: Research Funding, Speakers Bureau; Seattle Genetics: Consultancy; Verastem: Consultancy; Janssen: Consultancy, Speakers Bureau; Genentech: Speakers Bureau; Sanofi Genzyme: Speakers Bureau. Portell:BeiGene: Consultancy, Research Funding; Pharmacyclics: Consultancy; TG Therapeutics: Research Funding; Infinity: Research Funding; Roche/Genentech: Consultancy, Research Funding; Xencor: Research Funding; Bayer: Consultancy; Amgen: Consultancy; Janssen: Consultancy; Kite: Consultancy, Research Funding; Acerta/AstraZeneca: Research Funding; AbbVie: Research Funding. Rambaldi:Sanofi: Honoraria, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company); Astellas: Honoraria, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company); BMS/Celgene: Honoraria, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company); University of Milan: Current Employment; Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Support of parent study and funding of editorial support. Received travel support., Research Funding; Gilead: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel support from Gilead.; Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company). Research grant from Amgen Inc.; Omeros: Honoraria, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company); Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company); Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company). Advisory board and speaker fees from Pfizer.. Brander:Verastem: Consultancy, Honoraria, Other, Research Funding; NCCN: Other; Novartis: Consultancy, Other; Teva: Consultancy, Honoraria; Tolero: Research Funding; NCCN: Other; Novartis: Consultancy, Other; Teva: Consultancy, Honoraria; Tolero: Research Funding; AbbVie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other, Research Funding; ArQule: Consultancy, Other, Research Funding; Ascentage: Other, Research Funding; AstraZeneca: Consultancy, Honoraria, Other, Research Funding; BeiGene: Other, Research Funding; DTRM: Other, Research Funding; Genentech: Consultancy, Honoraria, Other, Research Funding; Juno/Celgene/BMS: Other, Research Funding; MEI Pharma: Other, Research Funding; Pharmacyclics LLC, an AbbVie Company: Consultancy, Honoraria, Other, Research Funding; Pfizer: Consultancy, Other; TG Therapeutics: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other, Research Funding. Rossi:Abbvie: Membership on an entity's Board of Directors or advisory committees; Daiichi Sankyo: Consultancy, Honoraria; Celgene: Membership on an entity's Board of Directors or advisory committees; Jazz: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees; Novartis: Other: Advisory board; Astellas: Membership on an entity's Board of Directors or advisory committees; Amgen: Honoraria; Pfizer: Membership on an entity's Board of Directors or advisory committees; Alexion: Membership on an entity's Board of Directors or advisory committees; Sanofi: Honoraria; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees. Coscia:Karyopharm Therapeutics: Research Funding; Gilead: Honoraria, Membership on an entity's Board of Directors or advisory committees; Shire: Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Abbvie: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Coombs:Abbvie: Consultancy, Honoraria; Genentech: Honoraria; AstraZeneca: Honoraria; MEI Pharma: Honoraria; LOXO Oncology: Honoraria; Octapharma: Honoraria; Novartis: Honoraria. Schuster:Novartis, Genentech, Inc./ F. Hoffmann-La Roche: Research Funding; AlloGene, AstraZeneca, BeiGene, Genentech, Inc./ F. Hoffmann-La Roche, Juno/Celgene, Loxo Oncology, Nordic Nanovector, Novartis, Tessa Therapeutics: Consultancy, Honoraria. Foà:Abbvie: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Roche: Membership on an entity's Board of Directors or advisory committees; Novartis: Speakers Bureau; Roche: Membership on an entity's Board of Directors or advisory committees; Incyte: Speakers Bureau; Janssen: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Cuneo:Astra Zeneca: Honoraria; Gilead: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Roche: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Abbvie: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Janssen: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Bosch:Jansen: Honoraria; Abbvie: Honoraria; Novartis: Honoraria; Astra Zeneca: Honoraria; Takeda: Honoraria; Celgene: Honoraria; Roche: Honoraria. Stamatopoulos:AstraZeneca: Honoraria; Janssen, Gilead, Abbvie: Honoraria, Research Funding. Ghia:Adaptive, Dynamo: Consultancy, Honoraria; Novartis: Research Funding; BeiGene: Consultancy, Honoraria; Janssen: Consultancy, Honoraria, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company), Research Funding; Celgene/Juno: Consultancy, Honoraria; Lilly: Consultancy, Honoraria; MEI: Consultancy, Honoraria; Sunesis: Consultancy, Honoraria, Research Funding; AbbVie: Consultancy, Honoraria, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company), Research Funding; Gilead: Consultancy, Honoraria, Research Funding; ArQule: Consultancy, Honoraria; Acerta/AstraZeneca: Consultancy, Honoraria. Mato:Adaptive: Consultancy, Research Funding; Janssen: Consultancy, Research Funding; AbbVie: Consultancy, Research Funding; BeiGene: Consultancy; LOXO: Consultancy, Research Funding; Genentech: Consultancy, Research Funding; AstraZeneca: Consultancy, Research Funding; Pharmacyclics LLC, an AbbVie Company: Consultancy, Research Funding; TG Therapeutics: Consultancy, Other: DSMB, Research Funding.

Abstract: IFNα is a biologic therapeutic agent with documented antitumoural effect in multiple myeloma. 15% of previously untreated myeloma patients achieve a clinical response to IFNα alone with a possible dose‐response relationship. A particularly good effect is noted in IgA myelomas treated with natural IFNα. A randomized study was started in April 1986 comparing melphalan/prednisone (MP) therapy with MP plus natural IFNα (MP/IFN) in untreated patients with multiple myeloma stages II and III. 220 patients had entered the study by autumn 1989. An interim report is given here. The response frequency was 48% in the MP group and 66% in the MP/IFN group ( P 〈 0·02). Stage II patients responded better to MP/IFN (76%) than to MP alone (48%) ( P 〈 0·01). No significant difference was noted for stage III patients. 91% of all IgA myelomas responded to MP/IFN and 52% to MP ( P 〈 0·01). The difference in response frequency of IgG and BJ myelomas between the two treatment groups was not statistically significant. The observation period is still too short to draw firm conclusions on survival. However, a statistically significant longer response duration time and survival from response ( P 〈 0·01) was noted for stage II patients.