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IntroductionMultiple myeloma (MM) is a plasma cell tumour with over 5800 new cases each year in the UK. The introduction of biological therapies has improved outcomes for the majority of patients with MM, but in approximately 20% of patients the tumour is characterised by genetic changes which confer a significantly poorer prognosis, generally termed high-risk (HR) MM. It is important to diagnose these genetic changes early and identify more effective first-line treatment options for these patients.Methods and analysisThe Myeloma UK nine OPTIMUM trial (MUKnine) evaluates novel treatment strategies for patients with HRMM. Patients with suspected or newly diagnosed MM, fit for intensive therapy, are offered participation in a tumour genetic screening protocol (MUKnine a), with primary endpoint proportion of patients with molecular screening performed within 8 weeks. Patients identified as molecularly HR are invited into the phase II, single-arm, multicentre trial (MUKnine b) investigating an intensive treatment schedule comprising bortezomib, lenalidomide, daratumumab, low-dose cyclophosphamide and dexamethasone, with single high-dose melphalan and autologous stem cell transplantation (ASCT) followed by combination consolidation and maintenance therapy. MUKnine b primary endpoints are minimal residual disease (MRD) at day 100 post-ASCT and progression-free survival. Secondary endpoints include response, safety and quality of life. The trial uses a Bayesian decision rule to determine if this treatment strategy is sufficiently active for further study. Patients identified as not having HR disease receive standard treatment and are followed up in a cohort study. Exploratory studies include longitudinal whole-body diffusion-weighted MRI for imaging MRD testing.Ethics and disseminationEthics approval London South East Research Ethics Committee (Ref: 17/LO/0022, 17/LO/0023). Results of studies will be submitted for publication in a peer-reviewed journal.Trial registration numberISRCTN16847817, May 2017; Pre-results.

Highlights • Lung cancer is the leading cause of cancer mortality worldwide. • Gold standard chemoradiotherapy is not deliverable for the majority of patients. • Radiation-induced DNA damage repair is an actionable mechanism of radioresistance. • Careful trial design is essential to elicit maximum impact on therapeutic index. • CONCORDE is a platform study of novel drug/radiotherapy combinations in lung cancer., Lung cancer is the leading cause of cancer mortality worldwide and most patients are unsuitable for ‘gold standard’ treatment, which is concurrent chemoradiotherapy. CONCORDE is a platform study seeking to establish the toxicity profiles of multiple novel radiosensitisers targeting DNA repair proteins in patients treated with sequential chemoradiotherapy. Time-to-event continual reassessment will facilitate efficient dose-finding.

Background: Outcomes for patients with ultra-high risk (UHiR) newly diagnosed multiple myeloma (NDMM) and patients with primary plasma cell leukemia (pPCL) remain unsatisfactory with current standard therapies. Traditional comparative trials randomising against a standard of care control arm are thus challenging for patients with UHiR NDMM or pPCL, and novel approaches to address their high unmet need are required. OPTIMUM/MUKnine (NCT03188172) is a 'digital comparator arm' trial for UHiR NDMM and pPCL patients with protocol defined outcome comparison against fully molecularly matched UHiR patients from the near-concurrent NCRI Myeloma XI/XI+ trial, the 'MyXI prior'. We report final analysis of the primary endpoint progression free survival (PFS) at 18 months for patients treated in OPTIMUM with Dara-CVRd induction, V-augmented ASCT and Dara-VRd consolidation, compared to the MyXI prior. Methods: Between Sep 2017 and Jul 2019, 472 patients from 39 UK hospitals with suspected NDMM or pPCL were screened. 107 patients with UHiR NDMM by central trial genetic (≥2 high risk lesions: t(4;14), t(14;16), t(14;20), gain(1q), del(1p), del(17p)) or gene expression SKY92 (SkylineDx) profiling, or with pPCL (circulating plasmablasts >20%) were identified and recruited to OPTIMUM. Patients received up to 6 cycles of Dara-CVRd induction, V-ASCT, followed by Dara-VRd consolidation 1 for 6 cycles (Cons1), Dara-VR consolidation 2 for 12 cycles and monthly Dara-R maintenance until progression. This is the final analysis of the primary trial endpoint progression-free survival (PFS) at 18 months comparing OPTIMUM with the MyXI prior of patients treated with CRd or carfilzomib-CRd (KCRd) induction, ASCT and R maintenance or observation, using a Bayesian framework. Secondary endpoints include PFS, OS, safety and quality of life. Results: At median follow-up of 27.1 months (95% CI 25.1-29.3), median PFS was not reached for OPTIMUM patients. PFS was superior at the pre-specified time point of 18 months for OPTIMUM patients with an estimate of 81.7% (95% CI: 74.2-89.1) versus 65.9% (95% CI: 57.3-74.4) for the MyXI prior (Figure 1). PFS at 18 months was consistently shorter for both CRd (64.5%; 95% CI: 53.8-75.3) and KCRd (68.3%; 95% CI: 54.0-82.5) treated patients compared with OPTIMUM. There was a 99.5% chance of superior PFS outcome with OPTIMUM therapy compared to the MyXI prior within the Bayesian framework; easily surpassing the 85% pre-specified threshold of sufficient evidence of activity. The difference between trial treatments increased over time: 6 month estimates were similar across all treatment arms with OPTIMUM 95.3% (95% CI: 91.3-99.3), MyXI KCRd 95.1% (95% CI: 88.5-100.0), MyXI CRd 93.5% (95% CI: 88.0-99.0), while 12 month estimates were similar for OPTIMUM with 87.5% (95% CI: 81.2-93.9) and MyXI KCRd 87.8% (77.8-97.8), but lower in CRd 81.7% (95% CI: 73.0-90.3). The majority (94%) of patients who started OPTIMUM Cons1 completed all 6 cycles of therapy. Most frequent grade 3/4 adverse events (AEs) during Cons1 included thrombocytopenia (27.9%), neutropenia (21%) and infection (19.8%), however, grade 4 events were rare ( Conclusions: OPTIMUM demonstrated a clear PFS benefit at 18 months for intensified Dara combination therapy pre- and post-ASCT for UHiR NDMM and pPCL over the MyXI prior. Improvement of comparative benefit over time suggests particular efficacy of Dara-VRd in maintaining responses post ASCT, a key challenge in UHiR MM. This is, to our knowledge, the first prospective digital comparator trial for MM; central screening of an all-comer population combined with robust, detailed molecular matching maintained reliability and limited biases. These results demonstrate a novel framework for accelerated comparative evidence generation for patients with high unmet clinical need. Figure 1 Figure 1. Disclosures Kaiser: BMS/Celgene: Consultancy, Other: Travel support, Research Funding; Janssen: Consultancy, Other: Educational support, Research Funding; GSK: Consultancy; Karyopharm: Consultancy, Research Funding; Pfizer: Consultancy; Amgen: Honoraria; Seattle Genetics: Consultancy; Takeda: Consultancy, Other: Educational support; AbbVie: Consultancy. Hall: Janssen: Research Funding; BMS/Celgene: Research Funding. Garg: University Hospital Leicester: Current Employment; Takeda Janssen Novartis Sanofi: Other: Travel Accommodations, Expenses; Amgen Janssen Novartis Sanofi Takeda: Honoraria. Jackson: J and J: Consultancy, Honoraria, Speakers Bureau; GSK: Consultancy, Honoraria, Speakers Bureau; takeda: Consultancy, Honoraria, Research Funding, Speakers Bureau; amgen: Consultancy, Honoraria, Speakers Bureau; celgene BMS: Consultancy, Honoraria, Research Funding, Speakers Bureau; oncopeptides: Consultancy; Sanofi: Honoraria, Speakers Bureau. Cook: BMS/Celgene: Consultancy, Research Funding; Janssen: Consultancy, Research Funding; Takeda: Consultancy, Research Funding; Sanofi: Consultancy; Karyopharm: Consultancy; Amgen: Consultancy. Pratt: Binding Site: Consultancy; Janssen: Consultancy; Takeda: Consultancy; Amgen: Consultancy; BMS/Celgene: Consultancy; Gilead: Consultancy. Drayson: Abingdon Health: Current holder of individual stocks in a privately-held company. Jenner: Janssen: Consultancy, Honoraria, Speakers Bureau; BMS/Celgene: Consultancy, Honoraria, Speakers Bureau; Pfizer: Consultancy; Takeda: Consultancy.

Background Outcome for patients with ultra high-risk (UHiR) newly diagnosed multiple myeloma (NDMM) or plasma cell leukemia (PCL) continues to be adverse, and UHiR patients are underrepresented in clinical trials. Recently, deepened responses have been reported for anti-CD38 monoclonal antibody combination therapy in NDMM. We report here protocol defined endpoints for the risk-stratified OPTIMUM/MUKnine (NCT03188172) trial for UHiR NDMM and PCL. Patients received daratumumab, cyclophosphamide, bortezomib, lenalidomide, dexamethasone (Dara-CVRd) induction and bortezomib-augmented HDMEL and ASCT. Early endpoints response and MRD from induction to day 100 post ASCT are reported. Methods Between Sep 2017 and Jul 2019, 472 patients with suspected NDMM from 39 UK hospitals were centrally molecularly screened. Of these, 107 patients were identified as having UHiR NDMM by trial genetic (≥2 high-risk lesions (double-hit): t(4;14), t(14;16), t(14;20), gain(1q), del(1p), del(17p)) or gene expression SKY92 (SkylineDx) profiling, or with PCL (circulating plasmablasts >20%) and enrolled in OPTIMUM. Induction consisted of 6 cycles of Dara-CVRd, HDMEL and ASCT augmented with bortezomib, followed by Dara-VR(d) consolidation for 18 cycles and Dara-R maintenance. Primary trial endpoints are minimal residual disease (MRD) status post ASCT and progression-free survival. Secondary endpoints include response, safety and quality of life. Results Median follow-up for the 107 patients in the safety population was 22.2 months (95% CI: 20.6 – 23.9). At baseline, 27% of patients were ISS stage I, 40% stage II and 32% stage 3 with 1.0% missing data and patient median age was 60 (range 35 to 78) years. 53% of patient tumors carried double-hit genetics and 77% a SKY92 high-risk signature. Two patients died early during induction due to myeloma-related infection. Bone marrow aspirates suitable for MRD assessment by flow (10-5 sensitivity) were available for 81% of patients at end of induction and 78% at D100 post ASCT. Responses in the ITT population at end of induction were 94% ORR with 22% CR, 58% VGPR, 15% PR, 1% PD, 5% timepoint not reached (TNR; withdrew, became ineligible or died) and at D100 post ASCT 83% ORR with 47% CR, 32% VGPR, 5% PR, 7% PD, 10% TNR. For PCL patients, response post ASCT was lower with 22% CR, 22% VGPR, 22% PR and 22% PD, 11% TNR. MRD status was 41% MRD-neg, 40% MRD-pos and 19% not evaluable post induction and 64% MRD-neg, 14% MRD-pos and 22% not evaluable at D100 post ASCT. Most frequent induction grade 3/4 AEs were neutropenia (21%), thrombocytopenia (12%) and infection (12%). Conclusions We report here high response and MRD-negativity rates with Dara-CVRd quintuplet induction and augmented ASCT in difficult-to-treat UHiR NDMM and PCL patients, with good tolerability and all-oral/subcutaneous deliverability. However, some early progressors highlight the ongoing need for innovation in UHiR MM and PCL.

8001 Background: Patients with ultra high-risk (UHiR) newly diagnosed multiple myeloma (NDMM) and patients with plasma cell leukemia (PCL) continue to have dismal outcomes and are underrepresented in clinical trials. Recently, improved responses with anti-CD38 monoclonal antibody combination therapy have been reported for NDMM patients. We report here outcomes for NDMM UHiR and PCL patients treated in the OPTIMUM/MUKnine (NCT03188172) trial with daratumumab, cyclophosphamide, bortezomib, lenalidomide, dexamethasone (Dara-CVRd) induction, augmented high-dose melphalan (HDMEL) and ASCT. With final analysis follow-up surpassed in Feb 2021, we report here early protocol defined endpoints from induction to day 100 post ASCT. Methods: Between Sep 2017 and Jul 2019, 107 patients with UHiR NDMM by central trial genetic (≥2 high risk lesions: t(4;14), t(14;16), t(14;20), gain(1q), del(1p), del(17p)) or gene expression SKY92 (SkylineDx) profiling, or with PCL (circulating plasmablasts > 20%) were included in OPTIMUM across 39 UK hospitals. Patients received up to 6 cycles of Dara-CVRd induction, HDMEL and ASCT augmented with bortezomib, followed by Dara-VR(d) consolidation for 18 cycles and Dara-R maintenance. Primary trial endpoints are minimal residual disease (MRD) status post ASCT and progression-free survival. Secondary endpoints include response, safety and quality of life. Data is complete but subject to further data cleaning prior to conference. Results: Median follow-up for the 107 patients in the safety population was 22.2 months (95% CI: 20.6 – 23.9). Two patients died during induction due to infection. Bone marrow aspirates suitable for MRD assessment by flow cytometry (10-5 sensitivity) were available for 81% of patients at end of induction and 78% at D100 post ASCT. Responses in the intention to treat population at end of induction were 94% ORR with 22% CR, 58% VGPR, 15% PR, 1% PD, 5% timepoint not reached (TNR; withdrew, became ineligible or died) and at D100 post ASCT 83% ORR with 47% CR, 32% VGPR, 5% PR, 7% PD, 10% TNR. MRD status was 41% MRDneg, 40% MRDpos and 19% not evaluable post induction and 64% MRDneg, 14% MRDpos and 22% not evaluable at D100 post ASCT. Responses at D100 post ASCT were lower in PCL with 22% CR, 22% VGPR, 22% PR, 22% PD, 12% TNR. Most frequent grade 3/4 AEs during induction were neutropenia (21%), thrombocytopenia (12%) and infection (12%). Grade 3 neuropathy rate was 3.7%. Conclusions: This is to our knowledge the first report on a trial for UHiR NDMM and PCL investigating Dara-CVRd induction and augmented ASCT. Response rates were high in this difficult-to-treat patient population, with toxicity comparable to other induction regimens. However, some early progressions highlight the need for innovative approaches to UHiR NDMM. Clinical trial information: NCT03188172.

Background Treatment of relapsed/refractory multiple myeloma (RRMM) remains challenging as durable remissions are achieved in patient sub-groups only. Identifying patients that are likely to benefit prior to or early after starting relapse treatments remains an unmet need. MUKseven is a trial specifically designed to investigate and validate biomarkers for treatment optimization in a 'real-world' RRMM population. Design In the randomized multi-center phase 2 MUKseven trial, RRMM patients (≥2 prior lines of therapy, exposed to proteasome inhibitor and lenalidomide) were randomized 1:1 to cyclophosphamide (500 mg po d1, 8, 15), pomalidomide (4 mg days 1-21) and dexamethasone (40 mg; if ≥75 years 20 mg; d1, 8, 15, 21) (CPomD) or PomD and treated until progression. All patients were asked to undergo bone marrow (BM) and peripheral blood (PB) bio-sampling at baseline, cycle 1 day 14 (C1D14, on-treatment) and relapse. For biomarker discovery and validation, IGH translocations were profiled by qRT-PCR, copy number aberrations by digital MLPA (probemix D006; MRC Holland), GEP by U133plus2.0 array (Affymetrix), PD protein markers by IHC and PB T-cell subsets by flow cytometry for all patients with sufficient material. Primary endpoint was PFS, secondary endpoints included response, OS, safety/toxicity and biomarker validation. Original planned sample size was 250 patients but due to a change in UK standard of care during recruitment with pomalidomide becoming available, a decision was made to stop recruitment early. Results In total, 102 RRMM patients were randomized 1:1 between March 2016 and February 2018. Trial entry criteria were designed to include a real-world RRMM population, permitting transfusions and growth factor support. Median age at randomization was 69 years (range 42-88), 28% of patients had received ≥5 prior lines of therapy (median: 3). Median follow-up for this analysis was 13.4 months (95% CI: 12.0-17.5). 16 patients remained on trial at time of analysis (median number of cycles: 19.5; range 8-28). More patients achieved ≥PR with CPomD compared to PomD: 70.6% (95% CI: 56.2-82.5%) vs. 47.1% (CI: 32.9-61.5%) (P=0.006). Median PFS was 6.9 months (CI: 5.7-10.4) for CPomD vs. 4.6 months (CI: 3.5-7.4) for PomD, which was not significantly different as per pre-defined criteria. Follow-up for OS is ongoing and will be presented at the conference. High-risk genetic aberrations were found at following frequencies: t(4;14): 6%, t(14;16)/t(14;20): 2%, gain(1q): 45%, del(17p): 13%. Non-high risk lesions were present as follows: t(11;14): 22%, hyperdiploidy: 44%. Complete information on all high-risk genetic markers was available for 71/102 patients, of whom 12.7% had double-hit high-risk (≥2 adverse lesions), 46.5% single-hit high-risk (1 adverse lesion) and 40.8% no risk markers, as per our recent meta-analysis in NDMM (Shah V, et al., Leukemia 2018). Median PFS was significantly shorter for double-hit: 3.4 months (CI: 1.0-4.9) vs. single-hit: 5.8 months (CI: 3.7-9.0) or no hit: 14.1 months (CI: 6.9-17.3) (P=0.005) (Figure 1A). GEP was available for 48 patients and the EMC92 high-risk signature, present in 19% of tumors, was associated with significantly shorter PFS: 3.4 months (CI: 2.0-5.7) vs. 7.4 (CI: 3.9-15.1) for EMC92 standard risk (P=0.037). Pharmacodynamic (PD) profiling of cereblon and CRL4CRBN ubiquitination targets (including Aiolos, ZFP91) in BM clots collected at baseline and C1D14 is currently ongoing. Preliminary results for the first 10 patients demonstrate differential change of nuclear Aiolos (Figure 1C), with a major decrease in Aiolos H-scores in 7/10 patients from baseline to C1D14 and reconstitution at relapse. T-cell PB sub-sets were profiled at baseline and C1D14 by flow cytometry. Specific sub-sets increased with therapy from baseline to C1D14, e.g. activated (HLA-DR+) CD4+ T-cells, as reported at last ASH. CD4+ T-cell % at baseline was associated with shorter PFS in these analyses in a multi-variable Cox regression model (P=0.005). PD and T-cell biomarker results will be updated and integrated with molecular tumor characteristics and outcome. Discussion Our results demonstrate that molecular markers validated for NDMM predict treatment outcomes in RRMM, opening the potential for stratified delivery of novel treatment approaches for patients with a particularly high unmet need. Additional immunologic and PD biomarkers are currently being explored. Disclosures Croft: Celgene: Other: Travel expenses. Hall:Celgene, Amgen, Janssen, Karyopharm: Other: Research funding to Institution. Walker:Janssen, Celgene: Other: Research funding to Institution. Pawlyn:Amgen, Janssen, Celgene, Takeda: Other: Travel expenses; Amgen, Celgene, Janssen, Oncopeptides: Honoraria; Amgen, Celgene, Takeda: Consultancy. Flanagan:Amgen, Celgene, Janssen, Karyopharm: Other: Research funding to Institution. Garg:Janssen, Takeda, Novartis: Other: Travel expenses; Novartis, Janssen: Research Funding; Janssen: Honoraria. Couto:Celgene Corporation: Employment, Equity Ownership, Patents & Royalties. Wang:Celgene Corporation: Employment, Equity Ownership. Boyd:Novartis: Consultancy, Honoraria; Janssen: Consultancy, Honoraria; Takeda: Consultancy, Honoraria; Amgen: Consultancy, Honoraria; Celgene: Consultancy, Honoraria. Pierceall:Celgene: Employment. Thakurta:Celgene: Employment, Equity Ownership. Cook:Celgene, Janssen-Cilag, Takeda: Honoraria, Research Funding; Janssen, Takeda, Sanofi, Karyopharm, Celgene: Consultancy, Honoraria, Speakers Bureau; Amgen, Bristol-Myers Squib, GlycoMimetics, Seattle Genetics, Sanofi: Honoraria. Brown:Amgen, Celgene, Janssen, Karyopharm: Other: Research funding to Institution. Kaiser:Takeda, Janssen, Celgene, Amgen: Honoraria, Other: Travel Expenses; Celgene, Janssen: Research Funding; Abbvie, Celgene, Takeda, Janssen, Amgen, Abbvie, Karyopharm: Consultancy.

Background High-risk myeloma patients have unsatisfactory outcomes with current treatments and are in urgent need of improved diagnostic and therapeutic strategies. We have recently validated specific markers predicting high-risk disease in newly diagnosed MM (NDMM), in particular double-hit with presence of ≥2 consensus high-risk markers t(4;14), t(14;16), t(14;20), del(1p), gain(1q), del(17p) (Shah V, et al., Leukemia 2018) and diagnostic GEP SKY92 high risk signature (Sherborne A, et al., IMW 2017). Diagnostic tests for these markers were implemented in the UK multi-center OPTIMUM: MUK9 trial to prospectively stratify therapy for high-risk NDMM. Trial design OPTIMUM: MUK9 is a phase 2 trial for transplant eligible NDMM, consisting of two inter-related protocols: a molecular screening protocol (MUK9A) and an interventional trial (MUK9B) for high-risk MM identified in MUK9A. Patients with suspected or confirmed MM fit for intensive therapy enrolled in MUK9A have central molecular profiling at ICR, London, of CD138-selected BM MM cells for translocations, copy number aberrations (qRT-PCR; MLPA P425, MRC Holland) and SKY92 signature status (MMprofiler; SkylineDx). If clinically indicated SOC therapy (VTD, max. 2 cycles) can be given whilst central results are generated. Patients found to have high-risk MM by double-hit and/or SKY92 are offered enrolment into MUK9B. All other patients receive SOC (VTD, HD-MEL+ASCT) for which clinical data is collected. Patients diagnosed with plasma cell leukemia (PCL) can be enrolled directly in MUK9B. MUK9B treatment consists of quintuplet daratumumab, cyclophosphamide, bortezomib, lenalidomide, dexamethasone (Dara-CVRd) induction (up to 6 cycles), bortezomib-augmented single HD-MEL+ASCT, Dara-VRd consolidation 1 (6 cycles), Dara-VR consolidation 2 (12 cycles) and Dara-R maintenance (until PD). Dose adjustments are permitted in order to maximize tolerability of long-term therapy. Patient reported outcomes (PRO) are recorded at baseline and throughout treatment. Response and MRD are centrally assessed (Birmingham, Leeds). Primary endpoint for MUK9A is feasibility of central molecular testing within 56 days turnaround time, which we report on here. Primary endpoint of MUK9B is treatment efficacy, comparing MUK9B PFS to near-concurrent molecularly matched high-risk patient outcomes from UK NCRI Myeloma XI using a Bayesian design. Secondary endpoints include safety, PFS2, MRD and OS and study of molecular evolution in high-risk disease. Results The protocol recruited 29/Sep/17 - 31/Jul/19 at 39 UK sites, achieving the recruitment target of 105 high-risk patients treated on MUK9B ahead of projections. At the time of analysis (12/Jul/19), 430 patients with suspected or confirmed NDMM have been recruited to MUK9A across 39 UK NHS hospitals. Of these, 376 (87%) patients were confirmed to have symptomatic MM (60.9% male; median age 61y (range 29-79)) as per updated IMWG diagnostic criteria (2014), including 9 (2%) PCL patients, with the remainder diagnosed as SMM/MGUS (31; 7%) or other (14; 3%). For 371 of the 376 symptomatic MM patients BM was received by the central laboratory and was of sufficient quality for profiling in 331 (89%) patients. Repeat samples were requested for all others and a sufficient sample received for 20/45 (44%). Central results were successfully reported within the pre-specified 56 day interval for all patients (median 17 days; IQR 13-22). Of 346 patients with a reported result, 128 (37.0%) have high-risk MM, with molecular characteristics mirroring Myeloma XI patients (Figure 1). PCL patients show expected characteristics as listed in Table 1. Basic demographics were not different between high-risk vs. non-high-risk. 101 high-risk patients have or are planning to enter MUK9B, 10 pending decision; 17 high-risk patients did not enter MUK9B, the majority due to ineligibility. 92 patients have started Dara-CVRD therapy. There are currently no safety concerns, the majority of patients are completing induction successfully; 1 patient stopped induction therapy due to adverse events. Updated results will be presented. Discussion Our data demonstrate feasibility of multi-center molecular stratified trial delivery for high-risk NDMM patients. These early trial results strongly support accelerated trial strategies for MM patient groups with high unmet need and rational drug development specifically for high-risk MM. Disclosures Jenner: Abbvie, Amgen, Celgene, Novartis, Janssen, Sanofi Genzyme, Takeda: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Hall:Celgene, Amgen, Janssen, Karyopharm: Other: Research funding to Institution. Walker:Janssen, Celgene: Other: Research funding to Institution. Croft:Celgene: Other: Travel expenses. Jackson:Celgene, Amgen, Roche, Janssen, Sanofi: Honoraria. Flanagan:Amgen, Celgene, Janssen, Karyopharm: Other: Research funding to Institution. Drayson:Abingdon Health: Consultancy, Equity Ownership. Owen:Celgene, Janssen: Consultancy; Celgene: Research Funding; Janssen: Other: Travel expenses; Celgene, Janssen: Honoraria. Pratt:Binding Site, Amgen, Takeda, Janssen, Gilead: Consultancy, Honoraria, Other: Travel support. Cook:Celgene, Janssen-Cilag, Takeda: Honoraria, Research Funding; Janssen, Takeda, Sanofi, Karyopharm, Celgene: Consultancy, Honoraria, Speakers Bureau; Amgen, Bristol-Myers Squib, GlycoMimetics, Seattle Genetics, Sanofi: Honoraria. Brown:Amgen, Celgene, Janssen, Karyopharm: Other: Research funding to Institution. Kaiser:Celgene, Janssen: Research Funding; Abbvie, Celgene, Takeda, Janssen, Amgen, Abbvie, Karyopharm: Consultancy; Takeda, Janssen, Celgene, Amgen: Honoraria, Other: Travel Expenses.

Background and aims Existing evidence regarding the effect of low-dose cyclophosphamide on immune cells in myeloma patients, in particular in combination with the IMiD® compound pomalidomide is limited. We present here for the first time changes in immune cell sub-group composition associated with the addition of cyclophosphamide to pomalidomide in the randomised MUKseven clinical trial. Material and Methods MUKseven is a randomised phase II study for relapsed or refractory myeloma (RRMM) patients comparing cyclophosphamide (500 mg po d1, 15, 21), pomalidomide and dexamethasone (CPd) versus standard pomalidomide and dex (Pd). Patients with ≥2 prior lines of therapy were randomised 1:1 to CPd or Pd and treated until disease progression. All patients underwent bone marrow sampling and peripheral blood collection, the latter for immune cell immunophenotyping at Cycle 1 Day 1 (C1D1; Baseline), C1D14 (on-treatment), C4D14 (on-treatment) and at disease progression. Peripheral blood (PB) T-cell populations were profiled using multicolor flow cytometry (MFC) designed to assess baseline and pharmacodynamic changes in subpopulations including helper, cytotoxic, naïve, memory, and activated/proliferating phenotypes (CD3, CD4, CD8, CD45RA, CD62L, HLA-DR, Ki67. T-cell sub-populations were defined and their respective % of total lymphocyte population used for downstream analyses. Results In total 102 evaluable RRMM patients were randomised, 51 each to CPd and Pd treatment arms, with comparable clinical baseline characteristics. Patients had received a median of 3 prior lines of treatment. Evaluable PB immune profiling data was available for 93 (91%) patients at Baseline, 83 (81%) at C1D14, 55 (54%) at C4D14 and 26 (25%) at progression. We observed trends for changes in baseline T-cell population composition with increasing numbers of prior lines of therapy. Specifically, mean % CD4+ T-cells decreased from 35% for patients with 2 prior lines (n=18) to 30% with 3 (n=33), 23% with 4 and 20% with ≥5 prior lines of treatment (n=27), whilst the % of CD8+ cells were similar, indicating potential differential cumulative effects of anti-myeloma therapy on T-cell populations. We compared changes in T-cell profiles longitudinally over trial treatment from baseline to C1D14 and C4D14 with summary statistics. Overall, there was a marked increase in activated (HLA-DR+) T-cells with therapy, with a 2-fold increase in mean proportion of activated CD4+ and CD8+ from 3.9% and 10.2% at baseline to 7.8% and 19.9% at C1D14 and 7.2% and 28.2% at C4D14, respectively (Figure 1). Trial treatment was associated with a shift in sub-populations within CD8+ T-cells in particular, with a relative % decrease in naïve (CD45RA+) sub-populations and increase in memory (CD45RA-) populations. To identify differences associated with cyclophosphamide treatment a regression analysis was conducted on the C1D14 time point accounting for the treatment a patient received and incorporating their baseline (C1D1) measurement. The mean% estimates for total T-cells (CD3+) at C1D14 were significantly higher for the CPd arm in comparison to Pd: 72.1% [95% CI: 66.5 - 73.6] vs. 64.2% [58.2 - 66.1] (P=0.004). Estimates for the Pd arm appeared similar to baseline [mean C1D1: 61.7%]. Mean% estimates for CD8+ and CD4+ cells were also significantly higher with CPd treatment at C1D14 compared to Pd: 37.2% [32.6 - 38.0] vs. 33.1% [28.5 - 33.7] (P=0.03) and 26.2% [21.6 - 27.0] vs. 21.8% [21.6 - 27.0] (P=0.016), respectively. Importantly, mean% estimates for activated (HLA-DR+) CD4+ cells were significantly higher for the CPd arm 10.1% [6.9 - 9.4] vs 8.1% [5.1 - 7.2] in the Pd arm (P =0.02). There was a trend for additional increase of activated CD8+ cells by addition of cyclophosphamide to Pd therapy (P=0.06). Discussion We demonstrate for the first time in a randomised trial using systematic longitudinal immune profiling that addition of cyclophosphamide to pomalidomide and dexamethasone is significantly associated with altered T-cell profiles and an increased proportion of activated T-cells. MUKseven clinical endpoint data are reported separately, with improved response rates observed for CPd vs. Pd. Correlation of immune profiles with clinical outcomes and tumour genetics will be presented at the conference when PFS outcome data will be mature. Disclosures Boyd: Novartis: Consultancy, Honoraria; Janssen: Honoraria, Other: Travel and Accommodation expenses; Celgene: Consultancy, Honoraria, Other: Advisory role. Garg:Janssen: Honoraria; Novartis: Other: travel support, Research Funding; Takeda: Other: Travel Grant; Amgen: Honoraria, Other: Travel Support. Pawlyn:Janssen: Honoraria, Other: Travel support; Celgene Corporation: Consultancy, Honoraria, Other: Travel support; Amgen: Consultancy, Honoraria, Other: Travel Support; Takeda Oncology: Consultancy, Other: Travel support. Pierceall:Celgene: Employment, Equity Ownership. Cook:Celgene Corporation: Consultancy, Honoraria, Research Funding, Speakers Bureau; Sanofi: Consultancy, Honoraria, Speakers Bureau; Amgen: Consultancy, Honoraria, Research Funding, Speakers Bureau; Glycomimetics: Consultancy, Honoraria; Bristol-Myers Squibb: Consultancy, Honoraria; Seattle Genetics: Honoraria; Janssen: Consultancy, Honoraria, Research Funding, Speakers Bureau; Takeda: Consultancy, Honoraria, Research Funding, Speakers Bureau; Janssen: Consultancy, Honoraria, Research Funding, Speakers Bureau. Thakurta:Celgene Corporation: Employment, Equity Ownership. Kaiser:Chugai: Consultancy; Takeda: Consultancy, Other: travel support; Celgene: Consultancy, Honoraria, Research Funding; Janssen: Consultancy, Honoraria; Bristol-Myers Squibb: Consultancy, Other: travel support; Amgen: Consultancy, Honoraria.