Kumar, Shaji

e20011 Background: Drug refractoriness is an important factor determining choice of next therapy and prognosis in multiple myeloma (MM). It is debatable whether refractoriness to a drug varies among patients (pts) with MM progressing on different administration schedules of the drug. Outcomes of MM pts refractory to different doses of lenalidomide have been previously described, but similar data about proteasome inhibitors (PIs) are limited. In this study, we assessed the impact of refractoriness to different schedules of bortezomib (V) on outcomes with subsequent therapies in MM pts. Methods: We retrospectively reviewed MM pts at our center diagnosed between January 2004 and December 2018, who progressed on/ after receiving first line therapy with V containing regimens. At first relapse, we divided pts into 3 groups- MM progressing on or within 60 days of receiving (1) 1-1.3 mg/m2 V once weekly or more frequently (Standard Dose Refractory), (2) 1-1.3 mg/m2 V once every 2 weeks or less frequently (Low Dose Refractory), and (3) MM progressing at least 60 days after stopping V (Not Refractory). In addition to V, we classified pts as being refractory to cyclophosphamide and immunomodulatory drugs (IMiDs) at first relapse. We classified salvage regimens into daratumumab (Dara), PI, IMiD, PI+IMiD, and VDTPACE like regimens. We then assessed progression free survival (PFS) and overall survival (OS) for next line therapy, and for next V containing therapy using Kaplan Meier and Cox models. Results: A total of 302 pts were included. Median age at diagnosis was 62 years and 60% pts were male. Overall, 23%, 31%, and 27% were International Staging System (ISS) stage I, II, and III respectively; 40% had high risk FISH as per mSMART. Of the 302 pts, 134 (44%) pts received another V containing regimen after the first line therapy at any time during the disease course. Using a multivariable Cox model to adjust for ISS, high risk FISH, refractoriness to other drugs, duration of first line therapy, and treatment received at relapse, the Not Refractory Group had a better PFS for both 2nd line therapy and the next V containing line of therapy, while no significant differences were seen between the Standard Dose Refractory and Low Dose Refractory groups. OS differences followed the same trend but were not statistically significant (Table). Conclusions: On multivariable analysis, the PFS did not differ among standard dose vs low dose refractory pts, and both were significantly inferior to pts not refractory to V. These data suggest that refractoriness to V might not be a dose dependent phenomenon. [Table: see text]

8056 Background: Multiple myeloma (MM) is preceded by monoclonal gammopathy of undetermined significance (MGUS). A transitional stage of smoldering multiple myeloma (SMM) can be identified between MGUS and MM. While MGUS carries a steady risk of progression of 1% per year, SMM is more heterogenous with nearly 40% of patients progressing in the first 5 years, 15% in the next 5 years, reaching the same low risk as MGUS after 10 years. SMM with its high risk of progression in the initial years after diagnosis presents a viable opportunity for early intervention. For implementing early intervention, the ability to identify SMM patients at the highest risk of progression is critical. This has led to the development of several risk stratification systems. Using these systems high risk SMM patients studied in phase 3 trials demonstrated delayed progression to MM and improved overall survival with early initiation of therapy. However, these approaches showed limited specificity exposing patients at lower risk of progression to therapy. To date, identifying high risk SMM patients and confirming disease stability in low risk SMM patients remain an important clinical need. Genomic instability has been shown to be a sensitive indicator of disease progression in cancer. Telomere dysfunction is an early event in genomic instability. The 3-dimensional spatial profiling of telomeres using TeloView technology allows for quantification of telomere dysfunction, and was shown to be instrumental in risk stratification of cancer patients generally, but particularly in selected hematological malignancies. Importantly, in a previous SMM proof-of-concept study telomeric parameters measured by TeloView technology was found to be significantly different between SMM patients who progressed to active MM within 2 years and those who remained stable for over 5 years. Methods: We analyzed a total of 162 SMM patients using TeloView technology. 88 patients were employed as training dataset in Receiver Operating Curve (ROC) modeling to develop a scoring model that stratifies individual SMM patients based on risk of progression to full stage MM. An additional cohort of 74 SMM patients was used for blind validation of the developed scoring model. Results: We report area-under-the-curve (AUC) in the ROC analysis of 0.8 (accuracy 80%) achieved by the scoring model developed using the training dataset. Furthermore, the independent blind validation achieved positive predictive value of 83% and negative predictive value of 71%, with sensitivity and specificity of 80% and 76% respectively. Conclusions: The result of this study supports presenting TeloView as an accurate prognostic biomarker which appears able to stratify SMM patients into their respective risk groups with high sensitivity and specificity. This will potentially allow for evidence-based treatment decisions for high risk SMM patients and confident monitoring of stable patients.

8051 Background: Patients with multiple myeloma (MM) that do not respond to initial therapy have worse outcomes compared to primary responders, and effective treatments are lacking in this population. However, the outcomes of primary refractory disease in the modern treatment era have not been studied. Methods: From 2007-2019, we reviewed MM patients treated with triplet/quadruplet therapy in our institution to assess the incidence of primary refractory disease and the impact of salvage therapies in this population. Primary refractory disease was defined as either progressive disease or stable disease at 4-6 cycles. The Kaplan-Meier estimates were used for survival probabilities. PFS and OS were calculated from MM diagnosis to progression, escalation/change of treatment, or death, respectively. For the primary refractory group, the second PFS and second OS were measured from the start of second-line therapy. The Cox regression model was used for multivariable analysis with the following variables (age, ISS, induction therapy, FISH, and bone marrow plasma cells at diagnosis). Results: We identified 1127 patients, of which 1086 were evaluated for hematologic response after 4-6 cycles. Of these, 93.3% (1013) had evidence of response, while 6.7% (73) had primary refractory disease. With a median OS of 50.7 months, patients with primary refractory disease had an increased risk for shorter survival in univariable and multivariable analysis (HR: 3.6, 95% CI = 2.61 – 4.96, HR = 3.89, 95% CI = 2.68 – 5.65, respectively). In subgroup analysis of primary refractory patients, the median second PFS and second OS from the first relapse were 11.9 months (95% CI: 8.7 – 17.3 months) and 43.4 (95% CI: 31.4– 75.9 months), respectively. Patients that received 2nd line ASCT had increased second PFS (20.9 vs. 8.1 months, respectively, p < 0.01) and second OS (74.7 vs. 31.3 months, respectively, p = 0.02) compared to patients that did not. Patients that took daratumumab as the second line did not have any significant survival differences compared to those who did not, p = NS. Conclusions: We conclude that early progression remains a significant factor for shorter OS in the current era, and salvage ASCT could be the most beneficial option for this population. [Table: see text]

8043 Background: Extramedullary Multiple Myeloma (EMM) has an aggressive clinical course and can present at diagnosis [primary EMM, (pEMM)] or relapse [secondary EMM, (sEMM)]. Here, we report clinical characteristics and outcomes of EMM, and predictive factors for the development of sEMM. Methods: We identified 299 patients with biopsy-proven EMM between 01/01/2000 and 12/31/2021. Patients with solitary plasmacytomas, paraskeletal MM and primary plasma cell leukemia were excluded. A 1:1 matched pair analysis (matched for year of diagnosis of MM for comparable follow-up and treatment eras) was performed to compare clinical characteristics and outcomes for patients with and without sEMM. Results: The median follow-up from the diagnosis of MM was 11.5 years (95%CI: 9.3-14.8). Of 299 patients, 204 (68%) patients had sEMM and 95 (32%) had pEMM, with largely comparable baseline characteristics (Table). The median overall survival (OS) from the diagnosis of sEMM was 0.7 (95% CI: 0.6-0.9) years compared to 3.6 (95%CI: 2.4-5.6) years for pEMM (p<0.0001). For sEMM, mutlvariable analysis (MVA) for OS identified visceral organ involvement (eg. liver, lung/pleura, brain, pancreas, etc.) to be associated with inferior OS [HR 1.6 (95% CI: 1.1-2.4), p=0.01]; high-risk cytogenetics (HR-CTG), ISS-3 stage, and age did not impact OS from sEMM. For pEMM, HR-CTG [HR 2.3 (95% CI 1.1 -4.8), p=0.03] and ISS-3 stage [HR 3.1 (95% CI 1.5-6.7), p=0.003] were associated with inferior OS on MVA whereas visceral EMM or age did not impact OS from pEMM. On univariate analysis, patients with sEMM were younger (median age 58.7 vs 61 years, p=0.006), had a higher proportion of 1q duplication (32% vs 17%, p=0.001), t(4;14) [16% vs 9%, p=0.047] and elevated LDH (30% vs 19%, p=0.04), compared to the matched cohort of patients without sEMM. On MVA, younger age at diagnosis, t(4;14) and 1q duplication at diagnosis of MM were independent predictors of development of sEMM. The median OS from diagnosis of MM was 5.4 years (95%CI: 4.1-6.2) for patients with sEMM versus 7.5 years (95% CI: 6.4-10.1; p <0.001) for the matched cohort. Secondary EMM was an independent poor prognostic marker for OS from the diagnosis of MM [HR 1.6 (95%CI: 1.2-2.1); p=0.004] in addition to age, ISS3 disease and HR-CTG. Conclusions: Outcomes of patients with EMM, especially sEMM, remain dismal. Patients with sEMM have higher rates of 1q duplication and t(4;14) at diagnosis of MM and carried an independent adverse prognosis in a matched cohort. [Table: see text]

8037 Background: Both daratumumab in combination with lenalidomide and dexamethasone (DRd) and bortezomib in combination with lenalidomide and dexamethasone (VRd) are endorsed by NCCN guidelines as preferred regimens for the treatment of transplant-ineligible (TIE) patients with newly diagnosed multiple myeloma (NDMM). DRd and VRd have each demonstrated superior efficacy relative to lenalidomide and dexamethasone (Rd) alone in the MAIA and SWOG S0777 trials, respectively, but have not been compared directly in a head-to-head trial. Naive comparisons of efficacy across the 2 trials may be biased because MAIA enrolled only TIE patients (median age 73 years), whereas S0777 enrolled a mixed transplant-not-intended (TNI) population, which included both TIE patients and patients choosing to defer/refuse frontline stem cell transplantation (median age 63 years). Methods: The present study leveraged individual patient-level data (IPD) from both trials to perform an anchored indirect treatment comparison of DRd vs VRd, adjusting for differences in trial eligibility criteria and baseline patient characteristics. Harmonized inclusion criteria (NDMM, age ≥65 years, ECOG performance status ≤2) were applied to both trial populations. Age ≥65 years served as a proxy for TIE status since S0777 enrolled a mixed TNI population. Propensity score (PS) reweighting was used to balance the 2 trial populations on key baseline prognostic factors including age, sex, ISS stage, ECOG performance status, hemoglobin, eGFR, lactate dehydrogenase (LDH) level, and cytogenetic risk. Missing data were addressed with multiple imputation. After alignment of inclusion criteria and PS reweighting, an anchored indirect comparison was performed wherein within-trial progression-free survival (PFS) hazard ratios (HRs) for DRd vs Rd and VRd vs Rd were estimated and used to make indirect inference about PFS for DRd vs VRd. Results: 727 MAIA participants and 198 S0777 participants were eligible for inclusion. After PS reweighting, the trial populations were balanced on the key baseline prognostic factors identified above (standardized difference < 0.1 for each). The adjusted PFS HRs were 0.53 (95% CI: 0.41–0.68; P< 0.0001) for DRd vs Rd in MAIA and 0.88 (0.63–1.23; P= 0.46) for VRd vs Rd in S0777. In the adjusted Rd-anchored indirect comparison, the PFS HR for DRd vs VRd was 0.60 (0.39–0.90; P= 0.02). Conclusions: In this adjusted indirect treatment comparison based on IPD from the MAIA and S0777 trials, PFS was significantly longer for DRd relative to VRd. In the absence of a head-to-head trial comparing DRd and VRd, the present study may help to inform treatment selection in TIE patients with NDMM.

8024 Background: Minimal residual disease (MRD) is prognostic for survival in multiple myeloma (MM). MRD is usually assessed in the bone marrow (BM) by flow cytometry or NGS. MRD by FDG PET/CT provides a global representation of the tumor burden, including response assessment of extramedullary disease. We examined MRD status in MM pts using both BM and PET/CT at Mayo Clinic. Methods: Medical records were reviewed retrospectively for MM pts who received CAR-T between 4/2018 and 12/2022. All PET/CT scans were assessed by radiologists. BM MRD was assessed by flow cytometry with a sensitivity of 10-5. Progression-free survival (PFS) and overall survival (OS) were analyzed by Kaplan-Meier method. Results: Among the 157 CAR-T pts, including 89 pts who received FDA-approved CAR-T, median age was 63 years, 59% (92/157) were males, 42% (66/157) had high risk cytogenetics with median of 5 prior lines of therapy, 36% (57/157) had plasmacytoma. Incidence of CRS was 83%, 5% grade ≥ 3 CRS. Incidence of ICANS was 19%, 4% grade ≥ 3 ICANS. CR/sCR rate was 37%. One hundred and thirty-seven pts (87%) had evaluable BM at month (mo) 1, 85% (117/137) were BM MRDneg at mo 1. Baseline demographics were comparable between the two groups except age, % BM plasma cells and use of bridging therapy. Among the MRDneg pts, CR/sCR rate was 44% (51/117) and 95% (111/117) had sFLC below normal. At median follow-up of 13.8 months, median PFS among pts with BM MRDneg at 1 mo was 12 mo (95% CI: 11, 30) vs 3 mo (95%CI: 2, 7) for BM MRDpos (p<0.001). Median OS among pts with BM MRDneg at 1 mo was 34 mo (95% CI: 24, NR) vs 22 mo (95%CI: 7, NA) for BM MRDpos (p<0.01). At month 1, 112 pts had both BM and PET/CT assessments available, 64/112(57%) were both BM MRDneg/PET MRDneg, 38/112 (34%) were MRDneg for either BM or PET and 10/112 (9%) were positive for both BM and PET (MRDpos/PET MRDpos). Baseline demographics except age were comparable between the 2 groups (Table). Rate of conversion from MRDpos to MRDneg was low. Rate of sustained BM and PET MRDneg at mo 12 was 44% (8/18). The median PFS and OS for BM MRDneg/PET MRDneg was significantly longer as compared to others (Table). Conclusions: Achieving FLC below normal, BM MRDneg and PET MRDneg at 1 month, regardless of IMWG response at that time, is prognostic for both PFS and OS in MM pts receiving CAR-T. Failure to achieve any of these confers poor prognosis. [Table: see text]

8022 Background: Extramedullary Multiple Myeloma (EMM) is an aggressive entity with a dismal prognosis. Immune effector therapies (IETs), including chimeric antigen receptor T-cell (CAR-T) therapies and bispecific T-cell engaging antibodies (BsAb), have demonstrated excellent efficacy in relapsed/refractory MM with limited data for efficacy in EMM. Here, we report the treatment outcomes for patients with EMM. Methods: We identified 299 patients with EMM diagnosed between 01/01/2000 and 12/31/2021 after excluding solitary plasmacytomas, paraskeletal MM and primary plasma cell leukemia. The IMWG criteria were used for response definition. Results: Of the 299 patients, 204 (68%) patients had secondary EMM (sEMM) and 95 (32%) patients had primary EMM (pEMM). For sEMM (n=204), the median progression free survival (PFS) with initial therapy was 2.9 (95% CI: 2.4-3.2) months. Initial treatment strategies for sEMM were heterogenous and demonstrated in the table; 44% patients achieved ≥partial response (PR) with initial treatment for sEMM. The median PFS in patients with ≥PR was 5.8 (95%CI: 4.5-6.9) months vs 1.8 (95%CI: 1.4-2; p <0.0001) months for <PR. For patients with pEMM (n=95), the median PFS was 12.9 (95% CI: 6.7-18) months; the median PFS was 17.4 (95%CI: 12.9-25.4) months for patients with ≥PR versus 1 month (95%CI: 0.8-2) in patients with <PR. Thirty patients (all sEMM and triple class refractory) were treated with IET after development of EMM: 18 with BCMA-directed CAR-T, 10 with BsAbs, and 2 with both CAR-T and BsAbs. In patients receiving CAR-T therapy, 75% (15/20) achieved ≥PR with 40% (n=8) achieving MRD negative (by flowcytometry) complete response. Fifteen (75%) patients receiving CAR-T had progressive disease (PD); 7 with systemic and EMM PD and 4 patients each with isolated EMM or systemic PD. The median PFS for patients treated with CAR-T was 4.9 months [3.1- not reached (NR)]. Among patients achieving a ≥PR with CAR-T, the median PFS was 5.8 (95%CI: 4.7-NR) months vs 1.4 months [(95%CI: 0.8-NR), p<0.001] for <PR. Among patients treated with BsAbs (10-BCMA, 1 each against FcRH5 and GPRC5D), 33% (4/12) achieved a ≥PR. Ten (83%) patients had PD on BsAb; 8 with both EMM and systemic PD and 1 patient each with isolated EMM or PD. The median PFS with BsAb was 2.9 months (95%CI: 2.2-NR). Conclusions: Patients with EMM continue to have dismal outcomes with conventional therapies. High response rates were noted with CAR-T therapy, but these tend to be short-lived. [Table: see text]

1533 Background: FDA-approved chimeric antigen receptor T-cell (CAR-T) and bispecific T cell engager (TCE) therapy are most commonly managed inpatient. Here we report our experience with hospital-based outpatient (HBO) management of patients (pts) receiving FDA-approved CAR-T or TCE and a predictive model for increased risk of early hospitalization (≤3 days post CAR-T). Methods: We reviewed the outcomes of pts who received FDA-approved CAR-T (axi-cel, brexu-cel, ide-cel, cilta-cel) or TCE (teclistamab) in the HBO unit between 3/2021 and 1/2023 at Mayo Clinic, Rochester. Results: HBO is closely integrated with inpatient practice and includes the same specialty trained clinical team. It is the first point of contact 24/7 for pts and triage evaluations. CAR-T and TCE are given on HBO followed by monitoring per REMS and as clinically needed until admission criteria is met. Remote patient monitoring (RPM) tools were used as part of outpatient monitoring. Out of 169 CAR-T pts, 87 (51%) were dosed with new indication/products (follicular lymphoma, mantle cell lymphoma, myeloma). Among those, 80 (92%) pts were dosed outpatient, among whom 21 (27%) were never hospitalized. CRS and ICANS incidences were comparable to that reported in registration studies. Median time to first admission from CAR-T infusion was 1 day (range, 0-9), with 31% (n=18/59) of admissions after day 3 post infusion. The most common cause of hospitalization was fever (n=40, 59%). Median length of hospital stay was 4 days (range, 1-49). Median time to tocilizumab (n=45, 80%), steroid (n=1, 2%), escalation of oxygen support (n=7, 12%), vasopressor (n=2, 3%), ventilator (n=1, 2%), hemodialysis (n=1, 2%) and ICU transfer (n=3, 5%) was 1 day (range, 0-31) after first admission. Use of bridging therapy, elevated CRP and LDH were predictive of early admission (ROC AUC 0.62). Four pts received teclistamab on HBO and enrolled in RPM. Data from more pts will be reported at ASCO. Conclusions: Our expanded study in CAR-T and TCE confirms that HBO is feasible and that CAR-T and TCE can be safely dosed outpatient. Approximately 31% of pts were admitted after 3 days from CAR-T infusion, and 27% of our pts were never admitted. Variables associated with aggressive disease can predict early hospitalization in pts receiving FDA-approved CAR-T. Extension of HBO practice to TCE is feasible.[Table: see text]

TPS8064 Background: Multiple myeloma (MM) remains an incurable disease. Combinations of established agents, including proteasome inhibitors (PIs), immunomodulatory drugs (IMiDs), and anti-CD38 antibodies, are used in all lines of therapy, but re-exposure to previously received classes of therapy is associated with decreasing response rates and duration of response (Moreau et al. 2021). BCMA-targeted agents have recently been approved for the treatment of patients with RRMM whose disease has been exposed or become refractory to PIs, IMIDs and anti-CD38 antibodies (triple-class exposed or refractory MM). Although effective, the majority of patients who respond to anti-BCMA agents eventually relapse. Proven salvage therapies for these patients are currently lacking and represent a new unmet medical need. Cevostamab is an immunoglobulin G1-based T-cell-engaging bispecific antibody that targets Fc receptor-homolog 5 (FcRH5) on myeloma cells and CD3 on T cells. Dual binding results in T-cell activation and potent killing of MM cells. In an ongoing Phase I study (GO39775; NCT03275103), cevostamab monotherapy showed promising activity in heavily pre-treated patients with RRMM, including those with prior exposure to anti-BCMA agents (Trudel et al. 2021). Methods: CAMMA 2 (CO43476; NCT05535244) is an open-label, multicenter Phase I/II trial evaluating cevostamab monotherapy in patients with RRMM who are triple-class refractory and have previously received an anti-BCMA agent. Prior anti-BCMA antibody-drug conjugates or chimeric antigen receptor (CAR) T cells are permitted in Cohorts A1 and B1, while prior anti-BCMA bispecific antibodies are allowed in Cohorts A2 and B2. In A1 and A2, cevostamab is administered by intravenous infusion and is initiated with step dosing (0.3mg on Cycle [C] 1 Day [D] 1 and 3.3mg on C1D2, D3, or D4 depending on the emergence and resolution of cytokine release syndrome [CRS] after the initial administration), with the target dose of 160mg given on C1D8 and on D1 of each subsequent 21-day cycle. Patients are hospitalized for the C1 administrations only and treatment is continued until disease progression or unacceptable toxicity occurs. CRS is managed per protocol based on the clinical presentation and may involve corticosteroid and tocilizumab treatment. Primary objectives are evaluation of efficacy (primary endpoint: objective response rate by investigator assessment using IMWG criteria) and safety. Secondary objectives include assessment of quality of life, pharmacokinetics, pharmacodynamics, and immunogenicity. Cohorts B1 and B2 will evaluate the efficacy and safety of cevostamab at the recommended Phase II dose in this setting. As of February 2023, enrolment into Cohorts A1 and A2 is ongoing. Clinical trial information: NCT05535244 .

Abstract Background Multiple laboratory tests are employed for detection of monoclonal proteins in patients and include serum protein electrophoresis (SPEP), immunofixation electrophoresis, free light chain (FLC) immunoassay, and mass spectrometry (Mass-Fix). Recently, reports on a drift in FLC quantitation results have been brought to light. Methods We studied a cohort of 16 887 patients whose sera were tested for a monoclonal protein by a FLC assay, serum protein electrophoresis, and Mass-Fix. This is a retrospective study designed to assess the impact of a drift on the performance of FLC ratio (rFLC) in groups of patients with and without detectable plasma cell disorders (PCDs). Results The results demonstrated that 63% of patients with monoclonal protein equal or higher than 2 g/L (by SPEP) had an abnormal rFLC (reference range 0.26–1.65). Conversely, 16% of patients with undetectable monoclonal protein by other methods (i.e., SPEP and Mass-Fix) who also had no record of treated PCD had an abnormal rFLC. In these cases, there was an imbalance in the number of kappa high rFLCs to lambda low rFLCs of 201 to 1. Conclusions The results of this study suggest decreased specificity of rFLC for a monoclonal kappa FLC in the 1.65 to 3.0 range.