TPS7582 Background: Relapsed and refractory multiple myeloma (RRMM) remains a significant therapeutic challenge, particularly among patients with genomic alterations in the RAS pathway (KRAS/NRAS mutations). These mutations occur in 60-70% of RRMM and are associated with aggressive disease and poor outcomes. Preclinical evidence suggests that dual inhibition of MEK and mTOR is required to effectively suppress oncogenic signaling in RAS dependent MM. This study evaluates the combination of the MEK inhibitor mirdametinib and the mTOR inhibitor sirolimus in patients with RAS-mutated RRMM. Methods: This is an open-label, single center, Phase 1b/2 study in adults with RRMM who are penta-class exposed and have no remaining standard therapeutic options. Patients must have RAS dependent MM as evidenced by a KRAS or NRAS mutation. Patients will be screened for these mutations at the NIH clinical center if unknown prior to referral. The phase 1b portion uses a standard 3+3 dose-escalation design to determine the recommended phase 2 dose (RP2D) of mirdametinib in combination with sirolimus. Phase 2 is a dose-expansion cohort using a Simon two-stage design to evaluate preliminary efficacy at the RP2D by overall response rate per the IMWG. Key eligibility criteria include adults aged ≥18 years with relapsed or refractory multiple myeloma per IMWG criteria, documented KRAS or NRAS mutation, prior exposure to a proteasome inhibitor, immunomodulatory agent, and anti-CD38 monoclonal antibody, ECOG performance status 0–2, and adequate organ function. Correlative studies include serial assessment of MAPK and mTOR pathway inhibition and pharmacodynamic biomarkers in peripheral blood and bone marrow samples. The study is actively enrolling at the NIH Clinical Center (NCT06876142), with a planned total enrollment of 54 patients. Clinical trial information: NCT06876142 .

Introduction: Patients with high-risk smoldering multiple myeloma (HR-SMM) have a risk of progression to multiple myeloma (MM) of ~75% in 5 years with median time to progression of 2 years.(Lakshman 2018)(Perez-Persona 2007) While active monitoring is commonly performed, randomized Phase 3 trials have demonstrated that early treatment with lenalidomide prolongs both PFS and OS in patients with HR-SMM.(Lonial 2019)(Mateos 2022) Building upon these results, Phase 2 studies utilizing lenalidomide combination regimens in HR-SMM showed high rates of undetectable MRD (56-84%).(Mateos 2019)(Kazandjian 2021)(Kumar 2022) Undetectable MRD is associated with longer PFS and OS in MM.(Landgren 2016)(Avet-Loiseau 2020) Lenalidomide's side effects such as rash, neutropenia, diarrhea, and second primary malignancies are significant in the otherwise asymptomatic population. Therefore, the optimal drug combination remains undetermined. The combination of daratumumab, carfilzomib, and dexamethasone (DKd) is a highly active regimen for relapsed refractory MM which spares immunomodulatory (IMiD) toxicities.(Chari et al 2019) This study aimed to evaluate the efficacy of DKd in patients with HR-SMM utilizing a response-adapted treatment duration (NCT04933539). The primary end point was the rate of undetectable MRD stringent complete responses (sCR) after induction. Design: This Phase 2, Simon 2-stage, investigator-initiated study enrolled HR-SMM patients based on the Mayo Clinic, PETHEMA, and/or Rajkumar, Mateos, and Landgren criteria. Patients received 8 cycles (28-days) of DKd [daratumumab 1800 mg SC per USPI, carfilzomib 20/56 mg/m2 days 1, 8, 15 and dexamethasone 40 mg days 1, 8, 15, 22]. Patients with persistently detectable MRD after 8 cycles of DKd received an additional 4 cycles. All responding patients then received daratumumab maintenance for 24 monthly cycles. Response was assessed by IMWG criteria after every cycle. MRD was assessed by multicolor flow cytometry (MRD sensitivity 10-5) after cycle 8, 12 (if applicable), and yearly. A pre-planned interim analysis was included to prevent futility based on the previously reported undetectable MRD rates of at least 55%. Results: Fourteen patients were enrolled between October 21, 2022, and January 22, 2024, with a median age of 58 years (range 29 -70). The cohort included 5 men (36%) and 9 women (64%). Six patients (43%) identified as African American/Black and 8 patients (57%) identified as White. Six patients (43%) had high risk cytogenetics (t(4;14), t(14;16), t(14;20), 1q gain, del17p). At a data cut off of July 1st, 2024, 2 patients are off study: one died of sudden cardiac death attributed to acute heart failure (cycle 4) and one withdrew consent due to long travel to the study site (cycle 1). One patient elected to stop therapy after 11 cycles due to frequent travel to the study site. Two patients remain on induction therapy and have not had MRD evaluation. The ORR (partial response or better) was 100% (95% CI, 77.19%-100%). VGPR or better was 92% (95% CI, 64.6 -99.9%) and sCR rate was 15% (95% CI, 4.33%-42.23%). Of 11 patients evaluable post induction, 3 (27.3%; 95% CI, 9.75%-56.56%) patients had no detectable MRD. Two patients had undetectable MRD sCR after 8 cycles (18% (95% CI, 5.14%-47.7%). Of the patients who remained MRD positive after cycle 8 and finished an additional 4 cycles (n=6), one patient developed undetectable MRD (16.7%; CI 95%, 3.01-56.35%) but remained in a VGPR. No patients have clinically progressed to overt MM. One patient experienced a grade 3 hematologic adverse event (AE), lymphopenia (n=1). Three patients (21%) had grade 3 or higher adverse events including hypertension (n=1), lung infection (n=1), and myocardial infarction (n=1). Conclusion: All patients with HR-SMM responded to DKd of which 92% had a VGPR or better. However, this study did not meet its pre-planned interim analysis goal of a 55% undetectable MRD rate. Most toxicities were low grade, but we did observe two significant cardiac adverse events. The patients remaining in the trial will be followed for safety, PFS, OS and completion of 24 cycles of daratumumab maintenance.

Background: Patients with high-risk smoldering multiple myeloma (HR-SMM) have a 5-year risk of progression to symptomatic multiple myeloma of approximately 75% and a median time to progression of less than 2 years (Lakshman et al., Blood Cancer J 2018) (Rajkumar et al., Blood 2015). We previously reported the primary results of our phase 2 trial of carfilzomib, lenalidomide, and dexamethasone followed by lenalidomide maintenance (KRd-R) as prevention of symptomatic multiple myeloma in patients with HR-SMM (Kazandjian et al., JAMA Onc 2021). Herein, we present follow-up data after all patients have completed lenalidomide maintenance to evaluate the durability of responses off therapy. Methods: Patients with HR-SMM based on the Mayo Clinic, PETHEMA, and/or Rajkumar, Mateos, and Landgren criteria were eligible for enrollment in this single-center phase 2 investigator-initiated study. Patients received eight 28-day cycles (induction) of carfilzomib, 20/36 mg/m 2, with dexamethasone 20/10 (days 1,2, 8, 9, 15, 16) and lenalidomide 25 mg (days 1-21), followed by 2 years of maintenance therapy with lenalidomide 10 mg (days 1-21). The primary endpoint was the rate of minimum residual disease negative complete responses (MRD negative CR) at the end of induction as assessed by multicolor flow cytometry (MRD sensitivity 10 -5). Secondary objectives included progression to overt clinical multiple myeloma (end-organ damage or myeloma-defining event) or death (clinical PFS) and biochemical progression (PD) by IMWG criteria (biochemical PFS). Results: A total of54 patients were enrolled and started treatment between May 29, 2012 and July 23, 2020. Full patient demographics and baseline disease characteristics were previously reported. (Kazandjian et al., JAMA Onc 2021) At the data cut-off of July 17, 2023, the median follow-up time was 60.2 months (range: 33.7 - 127.8). As previously reported, 38 patients (70.4%) achieved MRD negative CR by the end of induction. The median duration of MRD negative CR was 57.4 months (95% CI: 44.6 - 97.2). To date, durability of MRD negative CR has been observed up to 120.6 months and 21 patients (39%) have remained MRD negative for over 2 years (95% CI: 25.9 - 53.1%). (Figure 1) All patients attained a PR or better and the median duration of response has still not been reached. At 60 months, 75.1% of patients maintained their response (95% CI: 59.9 - 85.2%). The median clinical PFS has also not been reached. Only 5 out of 54 (9.3%; 95% CI: 3.1-20.3%) patients have progressed to clinical multiple myeloma. At 60 months, 92.7% of patients were free from clinical progression (95% CI: 78.1 - 97.9%). The probability of being free of clinical progression at 100 months was 78.9% (95% CI: 51.9 - 91.8%). While the median biochemical PFS has not been reached, patients who were MRD negative by the end of induction had significantly less risk of having biochemical progression compared to patients who still had measurable disease at completion of induction (median biochemical PFS NR vs. 41.8 (HR 0.168 (95% CI: 0.060 - 0.474) (P value < 0.0001) (Figure 2). As previously reported, KRd-R was well tolerated, with no grade 4 non-hematologic adverse events and manageable low-grade toxicities. Discussion: Treatment of patients with HR-SMM with KRd-R has led to deep and durable remissions. At a median of 5 years of follow-up, this trial has yet to reach a median clinical PFS, indicating success in preventing serious end organ damage. However, it is still unclear if the beneficial outcomes seen in HR-SMM interventional studies are due to treatment of more susceptible disease or inherently less aggressive disease. An abstract evaluating the genomic profile of patients from this trial has been submitted to the meeting separately. Future prospective trials must capture and eventually select HR profiles based on validated genomic signatures. This study suggests that patients who achieve MRD negative remissions after induction therapy have prolonged biochemical PFS. However, further follow-up time is needed to fully understand the rates of clinical PFS and OS. To evaluate if additional treatment duration to achieve MRD negativity would be beneficial we have designed a trial using daratumumab, carfilzomib, and dexamethasone utilizing an adaptive treatment duration based on MRD status for patients with HR-SMM which is currently enrolling participants (NCT04933539).

Background. Extramedullary disease (EMD) is recognized as an aggressive subentity of multiple myeloma (MM) with a need for novel therapeutic approaches. We therefore designed a proof-of-principle pilot study to evaluate the synergy between the combination of the anti-PD-L1, avelumab, and concomitant hypofractionated radiotherapy. Methods. This was a single-arm phase II Simon two-stage single center study that was prematurely terminated because of the COVID-19 pandemic after enrolling four patients. Key eligibility included patients with relapsed/refractory multiple myeloma (RRMM) who had exhausted or were not candidates for standard therapy and had at least one lesion amenable to radiotherapy. Patients received avelumab until progression or intolerable toxicity and hypofractionated radiotherapy to a focal lesion in cycle 2. Radiotherapy was delayed until cycle 2 to allow the avelumab to reach a study state, given the important observation from previous studies that concomitant therapy is needed for the abscopal effect. Results. At a median potential follow-up of 10.5 months, there were no objective responses, one minimal response, and two stable disease as best response. The median progression-free survival (PFS) was 5.3 months (95% confidence interval [CI]: 2.5-7.1 months), and no deaths occurred. There were no grade >= 3 and five grade 1-2 treatment-related adverse events. Conclusion. Avelumab in combination with radiotherapy for patients with RRMM and EMD was associated with very modest systemic clinical benefit; however, patients did benefit as usual from local radiotherapy. Furthermore, the combination was very well tolerated compared with historical RRMM treatment regimens.

Background: Multiple myeloma (MM) is the 2nd most common hematologic malignancy and remains incurable despite significant treatment advances over the last decade. Patients with relapsed/refractory multiple myeloma (RRMM), who have exhausted available therapies, have limited treatment options and a median survival as brief as 6 months (Richardson PG et al., Oncology 2010). Immune checkpoint inhibitors (CPI) have dramatically changed treatment paradigms in multiple cancers, with growing evidence that radiation therapy (XRT) may synergize with these agents via the abscopal effect. MM cells express high levels of PD-L1. Preclinical models have demonstrated rejection of murine myeloma when PD-L1 blockade was combined with XRT (Kearl TJ et al., Journal of Immunology 2013), as well as longer survival in myeloma-bearing mice compared to controls (Jing W et al., Journal for ImmunoTherapy of Cancer 2015). Early phase single arm clinical trials with combinations of immunomodulatory drugs (IMiDs) and CPI showed response rates between 33 and 76% (Pianko MJ et al., Stem Cell Investigation 2017)(San Miguel J et al., Blood 2015)(Badros A et al., Blood 2017). However, subsequent phase 3 studies revealed a potential safety signal of this combination (FDA 2017). Nonetheless, a subset of patients appear to attain durable responses (Badros A et al., Blood Advances 2019). CPI combined with other therapies such as XRT, that help to prime the immune system, hold great promise in the treatment of patients with RRMM. Herein, we describe our phase II study of avelumab, an anti-PD-L1 IgG1 antibody with potential antibody-dependent cellular cytotoxic properties, in combination with XRT in patients with RRMM. Methods: Trial Design: The primary endpoint of this trial is to assess the systemic response rate with the combination of avelumab and XRT in the treatment of extramedullary plasmacytomas or active lytic lesions in patients with RRMM using the 2016 IMWG response criteria. Secondary endpoints include determination of complete response rate, progression-free survival, and overall survival. Patients will undergo bone marrow biopsies and imaging (PET/CT and DW-MRI) at baseline, during disease response evaluations, and at the end of treatment. Treatment: Treatment consists of a 4-week lead-in with avelumab at a flat dose of 800mg IV every 2 weeks followed by concurrent XRT of 5Gy for 5 consecutive days directed toward the plasmacytoma/lytic lesion (Figure 1). Monotherapy avelumab, 800mg IV every 2 weeks, will continue indefinitely until disease progression or unacceptable toxicity. Analysis: This is a single arm trial with a Simon minimax two-stage phase II trial design that will enroll up to 27 patients. The first stage will enroll 13 evaluable patients, and if 0 of the 13 have a clinical response, then no further patients will be accrued due to futility. If 1 or more of the first 13 patients have a response, then accrual will continue until a total of 27 evaluable patients have been treated in the second stage. This will provide a two-sided alpha of 5% and a Power of 80% to rule out an ORR of 5% in favor of a response rate of 20%. Response fractions and time to event endpoints will be reported along with 90 and 95% two-sided confidence intervals with nominal p values. Eligibility: Patients must have previously treated relapsed MM or RRMM refractory to, ineligible for, or intolerant of, available myeloma therapies and have ≥ 1 extramedullary plasmacytoma and/or lytic lesion. Lesions must be amenable to, and clinically indicated for, treatment with localized XRT. Eligible patients must have documented evidence of progressive disease on, or after, their most recent regimen as defined by the IMWG criteria. They must have achieved at least a minimal response to one or more prior regimens. Exclusionary criteria include patients with: clinically unstable lesions where a delay in XRT may be detrimental; active autoimmune diseases or history of serious autoimmune-related disorders; uncontrolled intercurrent illnesses; concurrent use of immunosuppressant medications; and recent or current anti-cancer treatment prior to the first dose of avelumab. Current Enrollment: This study is actively enrolling patients to the first stage. At the time of this submission, 4 patients have been enrolled and have received at least one dose of trial therapy. Clinical trial registry number: NCT03910439. Figure Disclosures No relevant conflicts of interest to declare. OffLabel Disclosure: avelumab not approved in myeloma

Background: Early initiation of graft-versus-host disease (GvHD) is driven by donor alloreactive T-lymphocytes directed against recipient's histocompatibility antigens often overexposed during damage to tissues during the conditioning chemotherapy. Palifermin is a truncated form of human recombinant keratinocyte growth factor (KGF, also known as FGF7) that binds to FGF receptor 2b expressed in many epithelia including the epithelium of the epidermis, oral and GI mucosa, urothelium, and thymus, in which it exerts cytoprotective and regenerative effects. Palifermin also has immunomodulatory effects manifested as improvements in thymic function and downregulation of pro-inflammatory cytokines. Palifermin was FDA approved in 2004 at a dose of 60 mcg/kg/day (x3 consecutive days) for prevention of severe oral mucositis in hematologic malignancy patients receiving autologous hematopoietic stem cell transplant (HSCT). A single dose of 180 mcg/kg/day appears to have similar effects. In animal models, palifermin showed efficacy in controlling acute and chronic GvHD. However, subsequent clinical studies did not confirm efficacy for prevention of GvHD or for stimulation of functional thymus recovery using a dose/schedule based on the one that had been approved for autologous HSCT. We conducted a phase 1 study (NCT02356159) to determine the maximal safe single dose level of palifermin administered prior to starting transplant conditioning. Methods: This was an open-label, dose escalation study with standard 3+3 design. Four different dose levels of palifermin (180, 360, 540 and 720 µg/kg) were administered as a single dose on day -7 pretransplant. The reduced-intensity conditioning regimen (cyclophosphamide 1200 mg/m2/day IV and fludarabine 30 mg/m2/day IV), was given on days -6 to -3. Sirolimus, tacrolimus and low-dose post-HSCT methotrexate were used for GvHD prophylaxis. On day 0 all subjects received a peripheral blood stem cell (PBSC) graft from an unrelated donor (MUD) matched at least at HLA-A, -B, -C, -DRB1. Prior to transplant, subjects received one or two cycles of disease-specific lymphodepleting induction chemotherapy (EPOCH-F/R or FLAG). Subjects must have been ≥18 years old with a high-risk hematologic malignancy, Karnofsky performance status ≥60%, and acceptable organ function. The primary objective was to assess safety of palifermin and to recommend the phase 2 study dose. DLT was defined as non-relapse mortality before day 30 post-HSCT regardless of attribution to palifermin and non-hematologic grade ≥4 adverse events (AEs) occurring within 14 days after administration. AEs were recorded according to CTCAEv4. Results: From Oct 2015 to Mar 2019, 18 subjects were enrolled (NHL=7, AML/MDS=5, ALL/LBL=2, CML=2, MPN=1 and MM=1). Kahl's relapse risk was high, standard, and low in 15, 2, and 1 subject, respectively. Median HCT-CI score was 1 (0-4) with median age 47 years (21-66); 14 (78%) were males. Six subjects received dose level 1 (subject #3 was diagnosed with achalasia and grade 4 elevated lipase without radiological signs of pancreatitis, still attributed as DLT possibly related to palifermin). No DLTs occurred afterwards. Three subjects were enrolled onto each of dose levels 2, 3 and 4, with expansion of dose level 4 to 3 more subjects for additional safety exploration. Skin rash and Increased serum amylase or lipase were the most frequent AEs (Table 1A). Grade 3 increased serum amylase and grade 3 possible pancreatitis in subject #3 were the only SAEs attributed to study drug. All subjects engrafted successfully. Day 14 median CD3 and myeloid chimerism was 97% (36-100) and 99% (82-100), respectively, with the median time to 100% CD3 chimerism of 44 days (14-181). Table 1B lists occurrence of GvHD prior to any malignancy relapse. Four subjects had relapsed malignancy, for which 3 received DLI. After a median follow up of 28 months (2-55), 5 subjects have died, 2 malignancy relapses and 3 non-relapse related causes. Conclusion: Palifermin administered at dose four-times higher than previously given in humans is safe to use in patients undergoing MUD peripheral blood HSCT. MTD was not reached. Recommended phase 2 dose for examining efficacy in prevention of GvHD is 720 µg/kg. Disclosures Rubin: NIH/NCI: Ended employment in the past 24 months, Patents & Royalties; KGF/palifermin: Patents & Royalties; Paradigm Shift Therapeutics: Membership on an entity's Board of Directors or advisory committees. OffLabel Disclosure: Palifermin was FDA approved at a dose of 60 mcg/kg/day (x3 consecutive days) for prevention of severe oral mucositis in hematologic malignancy patients receiving autologous hematopoietic stem cell transplant (HSCT).

Background: HR-SMM is a plasma cell disorder with a 5-year risk of progression to symptomatic multiple myeloma (MM) of ~75% without therapy. Early treatment with novel therapies, may decrease the risk of progression and prolong survival as evidenced by studies (Quiredex and ECOG E3A06) comparing lenalidomide ± dexamethasone to observation. Randomized studies in MM have demonstrated that triplet are superior to doublet regimens and whole exome sequencing in HR-SMM suggests a more treatment-sensitive biology. Together, these support our initial pilot study (Korde et al, JAMA Onc 2015) in using effective therapy with KRd-R as early intervention. Given the favorable initial results of our pilot in terms of minimal residual disease (MRD) negativity rates, we designed a single-arm, phase 2 study with the primary objective of determining the rate of MRD negative complete remissions. Herein, we show that rates of MRD negativity are high and they are sustained with the use of KRd-R. Methods: Patients with HR-SMM (Mayo Clinic or PETHEMA models) received eight 28-day cycles of carfilzomib 20/36 mg/m2 IV days 1, 2, 8, 9, 15, 16; lenalidomide 25 mg PO days 1-21, and dexamethasone 20/10 mg days 1, 2, 8, 9, 15, 16, 22, 23. Transplant eligible patients underwent stem cell collection after 4 cycles of KRd and then resumed treatment without an intent for early high-dose melphalan with stem cell support (HDM-ASCT). After 8 cycles of KRd, patients transitioned to receive maintenance therapy with lenalidomide 10 mg PO days 1-21 for 24 additional cycles. Prophylactic antiviral and anticoagulation was mandated for all. MM laboratory evaluations were performed at the start of every cycle during KRd and every 3 cycles during -R and every 3 months during indefinite follow up. Bone marrow biopsies and PET/CTs were performed by the end of cycle 8 induction and then annually indefinitely. The primary objective was to determine the rate of MRD negative remissions by validated multi-color flow cytometry (≤10-5 sensitivity). Key secondary objectives included progression free survival (PFS) to symptomatic myeloma and biochemical progression per IMWG, duration of MRD negativity, overall response rate (ORR), and duration of response. Results: As of 7/15/2020, 52 patients meeting eligibility criteria were enrolled and their demographics and disease characteristics are shown in Table 1. With a median potential follow up of 27.3 months, the primary objective of MRD negative CR rate was 70.2% and the MRD negative ≥VGPR rate was 80.9%, Table 2. The median duration of MRD negativity was 5.5 years with 2 and 5 -year rates of 78% and 55%, respectively. The median time to progression to MM and time to biochemical progression was not reached with 90-month rates of 90% and 78%, respectively - 2 patients progressed to symptomatic MM and 4 patients biochemically. The ORR was 100% and 78% achieved a best response of stringent CR. No deaths occurred. All grade and Grade 3-4 treatment-related adverse events occurred in 90% and 33% of patients, respectively. Grade 3-4 toxicities occurring in >1 patient included neutropenia (19%), lymphopenia (13%), thromboembolism (12%), anemia (8%), rash (8%), leukopenia (6%), lung infection (6%), ALT increase (4%), diarrhea (4%), hyperglycemia (4%), hypophosphatemia (4%), and thrombocytopenia (4%). Other Grade 3-4 adverse events of interest occurring in ≤1 patient included atrial fibrillation, creatinine increase, dyspnea, febrile neutropenia, heart failure, hypertension, and neoplasm. Treatment discontinuation occurred in 4 patients; 3 due to toxicity and 1 due to patient withdrawal. Conclusions: Treatment of HR-SMM with KRd-R to prevent symptomatic MM resulted in an MRD negative CR rate of 70% with a median duration of 5.5 years. At the 5-year landmark, only 10% of patients developed MM which is favorable compared to historical rates with no treatment of ~75%. Alternative approaches using monotherapy lenalidomide (Lonial et al, JCO 2019) resulted in no CRs and a 5-year progression rate of 22% with a treatment discontinuation rate of 51% compared to 7% in our study. More aggressive approaches include GEM-CESAR (Mateos et al, ASH 2019) incorporating HDM-ASCT with KRd-R. Importantly, the rate of MRD negativity reported in GEM-CESAR was 56% compared to 70% in this study. Overall, the benefit compared to risk with KRd in SMM is very favorable. Future randomized trials will be needed to lock in this conclusion. Disclosures Korde: Amgen: Research Funding; Astra Zeneca: Other: Advisory Board. Mailankody:Physician Education Resource: Honoraria; PleXus Communications: Honoraria; Takeda Oncology: Research Funding; Janssen Oncology: Research Funding; Allogene Therapeutics: Research Funding; Juno Therapeutics, a Bristol-Myers Squibb Company: Research Funding. Manasanch:Quest Diagnostics: Research Funding; Sanofi: Research Funding; JW Pharma: Research Funding; Merck: Research Funding; Takeda: Honoraria; GSK: Honoraria; Sanofi: Honoraria; BMS: Honoraria; Adaptive Biotechnologies: Honoraria; Novartis: Research Funding. Bhutani:BMS: Other: Clinical trial funding to institute, Speakers Bureau; Amgen: Speakers Bureau; MedImmune: Other: Clinical Trial Funding to Institute; Janssen: Other: Clinical Trial Funding to Institute; Prothena: Other: Clinical Trial Funding to Institute; Sanofi Genzyme: Consultancy; Takeda: Other: Clinical trial funding to institute, Speakers Bureau. Landgren:Amgen: Consultancy, Honoraria, Research Funding; Pfizer: Consultancy, Honoraria; Merck: Other; Karyopharma: Research Funding; Merck: Other; Pfizer: Consultancy, Honoraria; Juno: Consultancy, Honoraria; Cellectis: Consultancy, Honoraria; Glenmark: Consultancy, Honoraria, Research Funding; Seattle Genetics: Research Funding; Juno: Consultancy, Honoraria; Janssen: Consultancy, Honoraria, Other: Independent Data Monitoring Committees for clinical trials, Research Funding; Karyopharma: Research Funding; Celgene: Consultancy, Honoraria, Research Funding; Glenmark: Consultancy, Honoraria, Research Funding; Takeda: Other: Independent Data Monitoring Committees for clinical trials, Research Funding; Janssen: Consultancy, Honoraria, Other: Independent Data Monitoring Committees for clinical trials, Research Funding; Celgene: Consultancy, Honoraria, Research Funding; Binding Site: Consultancy, Honoraria; Takeda: Other: Independent Data Monitoring Committees for clinical trials, Research Funding; BMS: Consultancy, Honoraria; Cellectis: Consultancy, Honoraria; BMS: Consultancy, Honoraria; Binding Site: Consultancy, Honoraria; Adaptive: Consultancy, Honoraria; Seattle Genetics: Research Funding. OffLabel Disclosure: carfilzomib, lenalidomide, and dexamethasone are not approved for smoldering myeloma.

Among patients who survive over two years post-allo-HSCT, cGVHD and subsequent cancers represent a significant source of morbidity and mortality. Long-term treatment with immunosuppressive agents and cGVHD-related immune dysregulation may promote the development of subsequent cancers. The burden of subsequent cancers has not yet been described in patients with the most severe manifestations of cGVHD, who likely represent a high-risk population. 439 patients were enrolled on the prospective NIH Chronic GVHD Natural History Study from 2004 to 2019, underwent one-week evaluation by subspecialists, and were scored in accordance with 2005 NIH criteria. Follow-up data were collected by annual survey in which patients self-reported cancer diagnoses and provided consent for confirmatory medical records. Cumulative incidence was estimated for non-melanoma skin cancer (NMSC) competing with death, relapse, or cancer other than NMSC and for cancer other than NMSC competing with death or relapse using the method of Gooley. Potential predictors of subsequent cancers including demographics, transplant characteristics, and cGVHD-related factors were assessed using Gray's test in univariable analysis and Cox proportional hazards models in multivariable analysis. Patients must have been free of post-transplant relapse, NMSC (for NMSC analyses only), and cancer other than NMSC at evaluation to be included in analysis. 22 NMSC and 19 cancers other than NMSC were observed among 205 eligible patients, with cumulative incidences at 60 months of 11.2% (95% CI: 6.9-16.7) and 7.3% (95% CI 4.1-11.8), respectively. The most common cancers other than NMSC were oral squamous cell carcinoma and melanoma (n=6 each). Factors associated with NMSC in univariable analysis were older age at transplant, older age at evaluation, having received sirolimus for cGVHD, having received extracorporeal photopheresis or psoralen-ultraviolet therapy for cGVHD as well as higher CRP, higher NK cell count, and greater BMI at evaluation. Only older age at transplant (HR=2.12; 95% CI: 1.35-3.31) and higher CRP (HR=9.61; 95% CI: 1.29-71.73) remained associated in the multivariable model. Factors associated with subsequent cancers other than NMSC in univariable analysis were T-cell depletion, lymphoid malignant indication for transplant, and increasing severity of oral cGVHD by NIH score. Only lymphoid malignant indication for transplant (HR=2.58; 95% CI: 1.31-5.07) remained significant in multivariable analysis. The association of CRP with NMSC may represent an effect of cGVHD-related inflammation, with CRP previously associated with cGVHD severity. Interestingly, sirolimus was associated with increased risk of NMSC despite its purported antineoplastic effects. One study has previously reported increased risk of NMSC in allo-HSCT recipients treated with sirolimus, however, numerous studies have reported that sirolimus reduces risk of NMSC in solid organ recipients. In this study population, sirolimus was often prescribed later in patients already with refractory cGVHD and adjustment for measures of disease severity attenuated this association in multivariable modeling. The association of lymphoid indication with cancers other than NMSC may be attributable to age as patients with lymphoid malignancies were older at transplant than those with other indications. Additionally, differences in pre-transplant therapies for lymphoid vs. other indications may also contribute to this observation. Post-transplant patients with cGVHD are at high risk of developing subsequent cancers, with higher incidence of NMSC than other cancers. This study identifies potential risk groups for subsequent cancers, highlights patients who may benefit from increased surveillance, and reiterates the need for effective cGVHD therapy to mitigate risks associated with long-term immunosuppression and immune dysfunction. Disclosures Cowen: UpToDate: Other: Royalties; Elsevier: Other: Royalties.

Chronic graft-versus-host disease (cGVHD) reduces relapse risk in patients with hematological malignancies treated with allogeneic hematopoietic stem cell transplant (allo-HSCT). Nevertheless, relapse remains a major barrier to treatment success. Better understanding of factors determining relapse risk in the cGVHD patient population may lead to development of improved strategies for malignancy control. We hypothesized that cGVHD-related factors would contribute to decreased risk of relapse in addition to other well-known transplant related factors. Patients (N=275) were enrolled on the NCI cross-sectional cGVHD natural history study (NCT00092235) and described using NIH criteria for disease severity and organ scoring. Subjects were subsequently followed for malignancy relapse and survival. Potential predictors of relapse were assessed for their association with risk of relapse using Gray's test. Cox proportional hazards modeling was performed to estimate the joint effect of factors on risk of relapse. Seventeen patients experienced relapse at a median follow-up of 85 months. 48-month cumulative incidence of relapse was 5.7% (95% CI 3.3-8.9%). Median progression-free survival was 156 months. Factors associated with increased risk of relapse in multivariable analysis included aggressive malignancy as an indication for transplant (HR 3.93, 95% CI 1.27-9.10), shorter time from transplant to cGVHD evaluation (HR 0.24, 95% CI 0.06-0.88), and higher number of prior lines of systemic immunosuppressive therapy for cGVHD (HR 0.34, 95% CI 0.12-0.98). Interestingly, conditioning intensity, T-cell depletion, HLA-match, female donor to male recipient, blood vs. marrow stem cell source, or malignancy remission status at transplant were not predictive of relapse in univariate or multivariate analyses. These data suggest an important inverse relationship between cGVHD severity and likelihood of relapse post-transplant. Most classical relapse predictors seem to be abrogated by these effects.