Gertz, Morie A.

e20016 Background: An elevated serum LDH level is an adverse prognostic factor in NDMM. However, this category includes quantitative serum LDH levels that range from just over the upper limit of normal (ULN) to levels that may be 2 or more-fold higher than the ULN. This binary classification of serum LDH level of “normal versus elevated” fails to discriminate between the different disease biology that exists among NDMM patients with elevated serum LDH levels. Thus, we attempted to further stratify NDMM patients by the level of their serum LDH and determine its impact on OS. Methods: The cohort included patients diagnosed with NDMM from the Mayo Clinic, Rochester from 2003 - 2017 who were treated with novel agent induction therapy and had serum LDH levels measured at the time of diagnosis. The serum LDH levels were stratified into three levels: Normal (LDH < 222 U/L), Elevated (LDH 223-444 U/L), and Very Elevated (LDH >444 U/L or >2x upper limit of normal). Survival analysis was performed using the Kaplan-Meier survival analysis and compared via the log-rank method. Results: The cohort consists of 1,196 NDMM patients with a median age of 65 (22 – 95). R-ISS classification and cytogenetic risk were available for 968 and 970 patients respectively. The median serum LDH level was (162 U/L (3- 1260)) and an elevated LDH was present in 199 patients (17%). The median OS for patients with normal (N = 997; 83%), elevated (N = 170; 13%) and very elevated (N = 29; 3%) LDH levels were 76 months, 57 months and 23 months respectively (P < 0.001). The impact of these different levels of LDH on OS by R-ISS stage and cytogenetic risk is shown in the Table. Conclusions: A very small subset of NDMM patients has very elevated LDH levels that confer an exceptionally poor OS irrespective of R-ISS stage and cytogenetic risk. Future studies elucidating their disease biology responsible for such poor OS outcomes are warranted.[Table: see text]

e20000 Background: In the novel agents’ era, refractoriness to induction in Multiple Myeloma (MM) is relatively rare. This population remain an unmet need and are often excluded from clinical trials. In the current era, chemotherapy-induced stem cell collections are used at Mayo Clinic in “poor responders” to induction, such as patients that progress prior to ASCT or patients with significant disease burden after induction. Methods: This is a retrospective study that includes all MM patients the underwent chemo-mobilization between January 2012 and September 2020 at Mayo Clinic. We compared our cohort to a cohort of 125 matched patients that were transplanted over the same time period and underwent mobilization with G-CSF and “on-demand” plerixafor. We matched the cohorts by level of response by IMWG at pre-transplant evaluation. Results: 125 newly diagnosed MM patients who received novel agents’ induction and had a poor response to induction were mobilized using IV intermediate-dose cyclophosphamide (83%) or VDT-PACE (17%) plus G-CSF and “on-demand” plerixafor. The median PFS and OS of the chemo-mobilized cohort were 16 months (95% CI 11-20) and 47 months (95% CI 37-71), respectively. Patients receiving chemo-mobilization had higher stem cell yields than the growth factor only cohort (median 9.88X106 cells/kg versus median 8.77X106 cells/kg, respectively (P<0.001)). The safety profile of chemo-mobilization was favorable, with no difference between the two groups in length of hospitalization during ASCT (P=0.95), days to neutrophil or platelet engraftment, and risk of bacteremia (P=0.38). 29% of the chemo-mobilized cohort and 66% of the matched cohort required plerixafor for adequate mobilization (P<0.001). Conclusions: Chemo-mobilization enhances stem cell collection in MM patients with a suboptimal response to induction and reduces the need for plerixafor without adversely impacting the post-transplant clinical course. [Table: see text]

8049 Background: The treatment paradigm of Waldenström macroglobulinemia (WM) continues to evolve as new therapies expand our options for this indolent and incurable disease. While more profound responses are generally associated with longer treatment-free intervals, the impact of depth of response from fixed duration therapy in WM patients' survival needs further evaluation. In this international, multicenter cohort study, we report the prognostic impact of depth of response in WM. Methods: 319 WM patients treated with frontline fixed duration therapy [Dexamethasone/Rituximab/Cyclophosphamide (DRC), Bendamustine/Rituximab (BR), or Bortezomib/Dexamethasone/Rituximab (BDR)] were included. Response at the completion of therapy (6 months) was used in a landmark analysis for progression-free survival (PFS), time to next treatment (TTNT), and overall survival (OS) (defined as time from 6 months post treatment response to event or censor). Response was defined by modified IWWM-6 criteria. Associations between clinical variables and outcomes were evaluated using Cox proportional-hazard models. Results: The median age at the time of treatment initiation was 64 years (range: 29-94), 59% were men, and risk category by International Prognostic Scoring System (IPSS)-WM was low (n=67, 23%), intermediate (n=83, 29%), and high-risk (n=141, 48%). Evaluable responses at 6 months from frontline therapy [DRC (n=105; 41%), BR (n=83; 32%), BDR (n=68; 27%)] were available in 256 patients and included in the landmark analysis. Median follow-up was 63 months (95% CI: 59-70). The rate of major response (PR or better) at 6 months was 74% for the entire cohort. Five-year PFS rates from completion of therapy for patients who attained major response vs. those who did not were 71% and 43%, respectively (p<0.001). Five-year TTNT rates for patients who attained major response vs. not were 84% and 54%, respectively (p<0.001). Five-year OS rates for patients who attained major response vs. not were 92% and 77%, respectively (p<0.001). In multivariable analyses including other WM prognostic factors evaluated at initiation of frontline therapy, attaining a major response at 6 months was associated with superior PFS (HR 0.33, p<0.001), TTNT (HR 0.23, p<0.001), and OS (HR 0.31, p=0.001–Table). Conclusions: Achieving a major response at 6 months after frontline chemoimmunotherapy emerges as a significant prognostic factor for PFS, TTNT and OS in patients with WM.[Table: see text]

2500 Background: Oncolytic virotherapy is a novel immunomodulatory therapeutic approach for relapsed refractory hematologic malignancies. The Indiana strain of Vesicular Stomatitis Virus was engineered to encode interferon beta (IFNβ) and sodium iodine symporter (NIS) to produce VSV-IFNβ-NIS. Virally encoded IFNβ serves as an index of viral proliferation and enhances host anti-tumor immunity. NIS was inserted to noninvasively assess viral biodistribution using SPECT/PET imaging. We present the results of the phase 1 clinical trial NCT03017820 of systemic administration of VSV-IFNβ-NIS among patients (pts) with relapsed refractory Multiple Myeloma (MM), T cell Lymphoma (TCL) and Acute myeloid Leukemia (AML). Methods: VSV-IFNβ-NIS was administered at 5x109 TCID50 (50% tissue culture infectious dose) dose level 1 to dose level 4, 1.7x1011 TCID50. The primary objective was to determine the maximum tolerated dose of VSV-IFNβ-NIS as a single agent. Secondary objectives were determination of safety profile and preliminary efficacy of VSV-IFNβ-NIS. Correlative objectives included monitoring viremia and virus shedding. Adverse events (AEs) are reported based on CTCAE V4; cytokine release syndrome (CRS) grading was based on Lee (Blood 2014) criteria. Results: 15 pts received VSV-IFNβ-NIS: MM (7), TCL(7) and AML(1); 3 pts were treated at each dose level (DL) 1 through 3 (respectively 0.05, 0.17, and 0.5 x 1011 TCID50), & 6 pts were treated at dose level 4 (1.7x1011 TCID50). There were no dose limiting toxicities. The most frequent grades 3 & 4 AEs were hematologic: lymphopenia (46.6 & 26.6%), neutropenia (13.3% & 6.7%). CRS grades 1 (6.7%) and 2 (46.6%) were the non-hematologic AEs of note; mostly at DL 4. Only 1 pt required transient pressor support. Responses were seen in pts with T cell lymphoma. At DL2, there was a partial response (PR) lasting 3 months in a pt, post 12 prior lines of therapy. At DL4 there was a 6 month PR in a pt with PTCL and another pt with cutaneous relapse of PTCL who enjoys an ongoing CR, more than 1 year post VSV infusion; both pts received 5 prior lines of therapy. Viremia was detected in all pts at the end of infusion only up to 72 hrs post infusion; no infectious virus was recovered in buccal swabs or urine. Neutralizing anti-VSV antibodies were present by day 29. IFN levels were detectable within 30 mins of infusion, peaking between 4 & 48 hrs. TCL pts mounted higher hIFNβ levels within 48 hrs; the pt with CR mounted peak hIFNβ response of 18213.3pg/ml at 48 hrs post infusion, 15-fold higher than any other pt. Conclusions: VSV-IFNβ-NIS can be safely administered by IV infusion among heavily pretreated pts with hematologic malignancies. VSV-IFNβ-NIS as a single agent appears to be most effective at DL4 among patients with TCL, with an ongoing CR in a patient at DL4 more than 1 year post administration. Future trials of combination strategies with immune-modulatory drugs are currently being planned. Clinical trial information: NCT03017820.

Abstract Comparative data guiding initial therapy for Waldenström macroglobulinemia (WM), an infrequently encountered non‐Hodgkin lymphoma, are sparse. We evaluated three commonly used rituximab‐based frontline regimens: rituximab‐bendamustine (R‐Benda); dexamethasone, rituximab, cyclophosphamide (DRC); and bortezomib, dexamethasone, rituximab (BDR) in 220 treatment‐naïve patients with WM, seen at Mayo Clinic between November 1, 2000 and October 31, 2019. The median follow‐up was 4.5 (95%CI: 4–5) years. The R‐Benda cohort (n = 83) demonstrated superior overall response rate (ORR: 98%), in comparison to DRC (n = 92, ORR: 78%) or BDR (n = 45, ORR: 84%) cohorts, p = 0.003. Similarly, longer progression‐free survival (PFS) was evident with R‐Benda use [median 5.2 vs. 4.3 (DRC) and 1.8 years (BDR), p < 0.001]. The time‐to‐next therapy (TTNT) favored R‐Benda [median, not‐reached, 4.4 (DRC) and 2.6 years (BDR), p < 0.001). These endpoints were comparable between the DRC and BDR cohorts. Overall survival (OS) was similar across the three cohorts, p = 0.77. In a subset analysis of 142 patients genotyped for MYD88 L265P mutation, the ORR, PFS and TTNT were unaffected by the patients' MYD88 signature within each cohort. In conclusion, ORR, PFS and TTNT with R‐Benda are superior compared to DRC or BDR in treatment‐naïve patients with active WM. The patient outcomes with any one of these three regimens are unaffected by the MYD88 L265P mutation status.

Abstract Patients with immunoglobulin M (IgM) light chain (AL) amyloidosis have a distinct clinical presentation compared with those with non-IgM amyloidosis. We hypothesized that differential immunoglobulin light-chain variable region (IGVL) gene usage may explain the differences in organ involvement, because IGVL usage correlates with organ tropism. IGVL usage was evaluated by mass spectrometry of amyloid deposits (IgM, n = 45; non-IgM, n = 391) and differed across the 2 groups. In the λ family, LV2-08 (13% vs 2%; P &lt; .001) and LV2-14 (36% vs 10%; P &lt; .001) usage was more common in IgM vs non-IgM amyloidosis, whereas LV1-44 (0% vs 10%; P = .02) and LV6-57 (2% vs 18%; P = .004) usage was less common. In the κ family, there was a trend toward higher KV4-01 (11% vs 4%; P = .06) usage in IgM amyloidosis. IGVL usage correlated with disease characteristics/organ tropism. LV2-14 (more common in IgM amyloidosis) has historically been associated with peripheral nerve involvement and lower light chain burden, which were more frequent in IgM amyloidosis. LV1-44 (less common in IgM), associated with cardiac involvement, was less frequent in IgM patients. LV6-57 (less common in IgM) is associated with t(11;14), which was less frequent in IgM patients. In conclusion, IGVL gene usage differs in patients with IgM vs non-IgM amyloidosis and may explain the distinct clinical presentation.

Abstract The immediate postautologous stem cell transplant (ASCT) period in multiple myeloma represents a unique opportunity for long-term disease control because many patients have eradicated most of their disease but also a challenge because it is characterized by the increase of immune subsets detrimental to tumor immunosurveillance. The impact of the tumor immune microenvironment (iTME) in post-ASCT outcomes is not known. In this study, we included 58 patients undergoing upfront ASCT and evaluated their cellular and humoral iTME with cytometry by time of flight (CyTOF) and luminex, respectively, at day +60 to 100 post-ASCT. We identified 2 cellular iTME patterns. Group 1 was enriched in T-cell subsets at the opposite ends of the spectrum of T-cell differentiation compared with the rest of the patients, that is, cells already terminally differentiated (immune senescent or exhausted) and naive T cells. This group had worse hematologic responses post-ASCT, inferior survival, and shorter time to hematologic progression independent of established risk factors. No differences in the humoral iTME were noted between the 2 groups. In addition, no differences in the cellular/humoral iTME were noted according to high-risk fluorescence in situ hybridization status, early or late relapse. Finally, males had higher levels of natural killer cells negative for CD16, a key receptor mediating antibody-dependent cell cytotoxicity, a major mechanism of antitumor efficacy by therapeutic antibodies such as elotuzumab. Our findings suggest that T-cell iTME dysfunction post-ASCT, some of which could be reversible (exhaustion), correlates with worse outcomes. These results could be used to guide rational selection of post-ASCT maintenance/consolidation approaches in these patients.

Abstract The utility of systemic light chain (AL) amyloidosis staging systems has been validated for newly diagnosed patients, but their role in restaging after treatment has not been explored. We designed this study to evaluate whether the currently used systems are of prognostic value at 3 and 6 months of starting first-line treatment, and whether stage migration from diagnosis impacts survival. This is a retrospective study including Mayo Clinic patients with AL amyloidosis diagnosed between 1 January 2006 and 30 June 2019; 536 and 204 patients had restaging data for at least 1 system at 3 and 6 months, respectively. Using modified Mayo 2004 staging at 3 months, median overall survival (OSs) were 11.8, 10.8, 4.6, and 1.1 years for stage I, II, IIIa, and IIIb, respectively. Using Mayo 2012, median OSs were 11.8, 9.0, 5.2, and 0.8 years for stage I, II, III, and IV, respectively. Using modified Mayo 2004 staging at 6 months, median OSs were not reached (NR), NR, 5.4, and 0.9 years for stage I, II, IIIa, and IIIb, respectively. Using Mayo 2012, OSs were NR, NR, 4.6, and 0.9 years for stage I, II, III, and IV, respectively. Worsening stage at 3 or 6 months was associated with worse survival than retaining baseline stage. In conclusion, the current staging systems can be used for restaging at 3 and 6 months from treatment initiation. Migration to higher stage predicts poor prognosis.