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There are no standard treatments to prevent or hasten the recovery from severe conditioning-regimen–induced thrombocytopenia occurring after autologous hematopoietic cell transplantation (auto-HCT). We conducted an open-label, single-arm pilot study of romiplostim, a thrombopoietin receptor agonist, to enhance platelet recovery in patients with multiple myeloma or lymphoma undergoing auto-HCT. All patients were treated weekly with romiplostim starting day +1 after auto-HCT until the platelet count was >50 × 109/L without transfusion. Compared with contemporary retrospective data from romiplostim-naïve patients (N = 853), romiplostim-treated patients (N = 59) had a similar median number of days of grade 4 thrombocytopenia or days requiring transfusions, time to platelet engraftment, and number of platelets transfusions during the auto-HCT. However, romiplostim-treated patients had enhanced platelet recovery to normal values beginning at approximately day +15. In matched cohort multivariable analyses, romiplostim treatment was associated with higher platelet counts by an average of 40 × 109/L (95% confidence interval (CI) (14, 67), P = .003) and 118 × 109/L (95% CI [84, 152], P

Although upfront autologous stem cell transplantation (ASCT) generally improves progression-free survival (PFS) in newly diagnosed multiple myeloma (NDMM), the overall survival (OS) benefit and optimal timing of ASCT are not well established. Patients with early response may be able to safely continue induction and avoid ASCT without compromised outcomes. We report an extended follow-up analysis of a phase 2 trial that randomized transplant-eligible patients with NDMM who responded to induction (50/65 patients) to continued induction or ASCT; median follow-up was 8.0 years. Patients had similar 8-year PFS (55% vs. 43%), 8-year OS (83% vs. 72%), and rates of at least very good partial response (72% vs. 84%) whether continuing induction of lenalidomide and dexamethasone (Ld arm) or receiving ASCT (Ld + ASCT arm) (ip/i = 0.5). Notably, over 50% of patients receiving continuous Ld had PFS of 5-10 years. These results suggest the need for prospective trials incorporating response-adapted therapeutic approaches to NDMM.STATEMENT OF PRIOR PRESENTATIONPresented in abstract form (interim analysis) at the 56th annual meeting of the American Society of Hematology (San Francisco, CA, 6 December 2014) and at the 57th annual meeting of the American Society of Hematology (Orlando, FL, 3 December 2015).

Purpose: Sustained minimal residual disease (MRD) negativity is associated with long-term survival in multiple myeloma. The gut microbiome is affected by diet, and in turn can modulate host immunity, for example through production of short-chain fatty acids including butyrate. We hypothesized that dietary factors affect the microbiome (abundance of butyrate-producing bacteria or stool butyrate concentration) and may be associated with multiple myeloma outcomes. Experimental Design: We examined the relationship of dietary factors (via a food frequency questionnaire), stool metabolites (via gas chromatography–mass spectrometry), and the stool microbiome (via 16S sequencing - α-diversity and relative abundance of butyrate-producing bacteria) with sustained MRD negativity (via flow cytometry at two timepoints 1 year apart) in myeloma patients on lenalidomide maintenance. The Healthy Eating Index 2015 score and flavonoid nutrient values were calculated from the food frequency questionnaire. The Wilcoxon rank sum test was used to evaluate associations with two-sided P < 0.05 considered significant. Results: At 3 months, higher stool butyrate concentration (P = 0.037), butyrate producers (P = 0.025), and α-diversity (P = 0.0035) were associated with sustained MRD negativity. Healthier dietary proteins, (from seafood and plants), correlated with butyrate at 3 months (P = 0.009) and sustained MRD negativity (P = 0.05). Consumption of dietary flavonoids, plant nutrients with antioxidant effects, correlated with stool butyrate concentration (anthocyanidins P = 0.01, flavones P = 0.01, and flavanols P = 0.02). Conclusions: This is the first study to demonstrate an association between a plant-based dietary pattern, stool butyrate production, and sustained MRD negativity in multiple myeloma, providing rationale to evaluate a prospective dietary intervention.

Cellular therapies including allogeneic hematopoietic cell transplant (allo-HCT) and autologous hematopoietic cell transplant (auto-HCT) and chimeric antigen receptor (CAR) T-cell therapy render patients severely immunocompromised for extended periods after therapy, and data on responses to COVID-19 vaccines are limited. We analyzed anti–SARS-CoV-2 spike IgG Ab (spike Ab) titers and neutralizing Ab among 217 recipients of cellular treatments (allo-HCT, n = 149; auto-HCT, n = 61; CAR T-cell therapy, n = 7). At 3 months after vaccination, 188 patients (87%) had positive spike Ab levels and 139 (77%) had positive neutralization activity compared with 100% for both in 54 concurrent healthy controls. Time from cellular therapy to vaccination and immune recovery post–cellular therapy were associated with response. Vaccination against COVID-19 is an important component of post–cellular therapy care, and predictors of quantitative and qualitative response are critical in informing clinical decisions about optimal timing of vaccines and the requirement for booster doses.Significance:Identifying predictors of response to vaccination against SARS-CoV-2 in patients following cellular therapy is critical to managing this highly vulnerable patient population. To date, this is the most comprehensive study evaluating quantitative and qualitative responses to vaccination, providing parameters most predictive of response and potentially informing booster vaccination strategies.See related article by Chung et al., p. 568.This article is highlighted in the In This Issue feature, p. 549

Coronavirus disease-19 (COVID-19) vaccine response data for patients with hematologic malignancy, who carry high risk for severe COVID-19 illness, are incomplete. In a study of 551 hematologic malignancy patients with leukemia, lymphoma, and multiple myeloma, anti–SARS-CoV-2 spike IgG titers and neutralizing activity were measured at 1 and 3 months from initial vaccination. Compared with healthy controls, patients with hematologic malignancy had attenuated antibody titers at 1 and 3 months. Furthermore, patients with hematologic malignancy had markedly diminished neutralizing capacity of 26.3% at 1 month and 43.6% at 3 months, despite positive seroconversion rates of 51.5% and 68.9% at the respective time points. Healthy controls had 93.2% and 100% neutralizing capacity at 1 and 3 months, respectively. Patients with leukemia, lymphoma, and multiple myeloma on observation had uniformly blunted responses. Treatment with Bruton tyrosine kinase inhibitors, venetoclax, phosphoinositide 3-kinase inhibitors, anti-CD19/CD20–directed therapies, and anti-CD38/B-cell maturation antigen–directed therapies substantially hindered responses, but single-agent immunomodulatory agents did not.Significance:Patients with hematologic malignancy have compromised COVID-19 vaccine responses at baseline that are further suppressed by active therapy, with many patients having insufficient neutralizing capacity despite positive antibody titers. Refining vaccine response parameters is critical to guiding clinical care, including the indication for booster vaccines, for this vulnerable population.See related article by Tamari et al., p. 577.This article is highlighted in the In This Issue feature, p. 549

3A: Anti-SARS-CoV-2 spike IgG titers by different cutoffs Supplemental Table 3B: Neutralization Ab >30% threshold when using different cutoffs of anti-SARS-CoV-2 spike IgG response

50 Anti-SARS-CoV-2 spike IgG, 30 Neutralizing antibodies

2A- MVA for the whole cohort 2B-MVA for patients who underwent allo-HCT only

Supplemental article file

moDC stimulated NK cells retain surface expression of the gamma chain receptor despite the presence of JAK inhibitors.

TG101348 and ruxolitinib inhibit JAK2 mediated STAT5 and STAT3 phosphorylation.

Inhibition of JAK1/2 with ruxolitinib reduces NK cell numbers and function among treated patients with myeloproliferative neoplasm (MPN).

Supplementary Figure S1. Volcano plot showing the difference in the relative abundance of butyrate producers between sustained MRD negative and MRD positive/non-sustained MRD negative.

Purpose:Sustained minimal residual disease (MRD) negativity is associated with long-term survival in multiple myeloma. The gut microbiome is affected by diet, and in turn can modulate host immunity, for example through production of short-chain fatty acids including butyrate. We hypothesized that dietary factors affect the microbiome (abundance of butyrate-producing bacteria or stool butyrate concentration) and may be associated with multiple myeloma outcomes.Experimental Design:We examined the relationship of dietary factors (via a food frequency questionnaire), stool metabolites (via gas chromatography–mass spectrometry), and the stool microbiome (via 16S sequencing - α-diversity and relative abundance of butyrate-producing bacteria) with sustained MRD negativity (via flow cytometry at two timepoints 1 year apart) in myeloma patients on lenalidomide maintenance. The Healthy Eating Index 2015 score and flavonoid nutrient values were calculated from the food frequency questionnaire. The Wilcoxon rank sum test was used to evaluate associations with two-sided P < 0.05 considered significant.Results:At 3 months, higher stool butyrate concentration (P = 0.037), butyrate producers (P = 0.025), and α-diversity (P = 0.0035) were associated with sustained MRD negativity. Healthier dietary proteins, (from seafood and plants), correlated with butyrate at 3 months (P = 0.009) and sustained MRD negativity (P = 0.05). Consumption of dietary flavonoids, plant nutrients with antioxidant effects, correlated with stool butyrate concentration (anthocyanidins P = 0.01, flavones P = 0.01, and flavanols P = 0.02).Conclusions:This is the first study to demonstrate an association between a plant-based dietary pattern, stool butyrate production, and sustained MRD negativity in multiple myeloma, providing rationale to evaluate a prospective dietary intervention.

Purpose: We compared the efficacy of human Langerhans cells (LC) as tumor immunogens in vivo with monocyte-derived dendritic cells (moDC) and investigated how interleukin 15 (IL15) supports optimal DC-stimulated antitumor immunity.Experimental Design: American Joint Committee on Cancer stage III/IV melanoma patients participated in this first clinical trial comparing melanoma peptide-pulsed LC with moDC vaccines (NCT00700167, www.ClinicalTrials.gov). Correlative studies evaluated mechanisms mediating IL15 support of DC-stimulated antitumor immunity.Results: Both DC vaccines were safe and immunogenic for melanoma antigens. LC-based vaccines stimulated significantly greater tyrosinase–HLA-A*0201 tetramer reactivity than the moDC-based vaccines. The two DC subtypes were otherwise statistically comparable, in contrast to extensive prior data in vitro showing LC superiority. LCs synthesize much more IL15 than moDCs and stimulate significantly more antigen-specific lymphocytes with a cytolytic IFN-γ profile even without exogenous IL15. When supplemented by low-dose IL15, instead of IL2, moDCs stimulate 5 to 6 logs more tumor antigen–specific effector memory T cells (TEMRA) over 3 to 4 weeks in vitro. IL2 and IL15 can be synergistic in moDC stimulation of cytolytic T cells. IL15 promotes T-cell expression of the antiapoptotic bcl-2 and inhibits candidate regulatory T-cell (Treg) expansion after DC stimulation, countering two effects of IL2 that do not foster tumor immunity.Conclusions: MoDC-based vaccines will require exogenous IL15 to achieve clinical efficacy. Alternatively, LCs can couple the endogenous production of IL15 with potent T-cell stimulatory activity. Optimization of full-length tumor antigen expression for processing into multiple immunogenic peptides for presentation by both class I and II MHC therefore merits emphasis to support more effective antitumor immunity stimulated by LCs. Clin Cancer Res; 17(7); 1984–97. ©2011 AACR.

Supplementary Figures S1-S3.

Patients treated with cytotoxic therapies, including autologous stem cell transplantation, are at risk for developing therapy-related myeloid neoplasms (tMN). Pre-leukemic clones (i.e., clonal hematopoiesis; CH) are detectable years before the development of these aggressive malignancies, though the genomic events leading to transformation and expansion are not well-defined. Here, leveraging distinctive chemotherapy-associated mutational signatures from whole-genome sequencing data and targeted sequencing of pre-chemotherapy samples, we reconstruct the evolutionary life-history of 39 therapy-related myeloid malignancies. A dichotomy is revealed, in which neoplasms with evidence of chemotherapy-induced mutagenesis from platinum and melphalan are hypermutated and enriched for complex structural variants (i.e., chromothripsis) while neoplasms with non-mutagenic chemotherapy exposures are genomically similar to de novo acute myeloid leukemia. Using chemotherapy-associated mutational signatures as temporal barcodes linked to a discrete clinical exposure in each patient's life, we estimate that several complex events and genomic drivers are acquired after chemotherapy is administered. For patients with prior multiple myeloma who were treated with high-dose melphalan and autologous stem cell transplantation, we demonstrate that tMN can develop from either a reinfused CH clone that escapes melphalan exposure and is selected following reinfusion, or from TP53-mutant CH that survives direct myeloablative conditioning and acquires melphalan-induced DNA-damage. Overall, we reveal a novel mode of tMN progression that is not reliant on direct mutagenesis or even exposure to chemotherapy. Conversely, for tMN that evolve under the influence of chemotherapy-induced mutagenesis, distinct chemotherapies not only select pre-existing CH, but also promote the acquisition of recurrent genomic drivers.

Monoclonal immunoglobulin deposition disease (MIDD), often associated with plasma cell dyscrasias, predominantly affects the kidneys. In this disease, hematologic response (HR) to treatment can be reliably assessed by International Myeloma Working Group (IMWG) consensus criteria, while uniform criteria for assessing renal response are lacking. We report a retrospective analysis of renal outcomes among 34 patients with MIDD. With most patients treated with bortezomib and autologous stem cell transplantation, 26 of 28 (94%) achieved very good partial HR or better. We demonstrate that both IMWG (based on estimated glomerular filtration rate, eGFR) and amyloid (based on proteinuria) criteria are needed to capture renal response: among 28 evaluable patients, 6 (21%) had isolated proteinuria, while 13 (46%) had isolated decreased eGFR. Using both criteria, which were concordant in patients with both decreased eGFR and proteinuria, 22 of 28 patients (79%) achieved a renal response, including 2 of 7 discontinuing dialyses. All 6 patients (100%) with isolated proteinuria and 7 of 13 (54%) with isolated decreased eGFR achieved renal response, suggesting that isolated proteinuria is an early manifestation of MIDD associated with reversible renal damage. Baseline eGFR predicted renal response (p = .02 by quartile) and survival (p = .02), while HR (CR vs. non-CR) did not, probably because of high HR rate. With a median follow-up of 110 months, the median overall survival was 136 months (95% CI: 79-NR) and median renal survival had not been reached. Prospective studies using uniform renal response criteria are needed to optimize the management of MIDD.

Coronavirus disease-19 (COVID-19) vaccine response data for patients with hematologic malignancy, who carry high risk for severe COVID-19 illness, are incomplete. In a study of 551 hematologic malignancy patients with leukemia, lymphoma, and multiple myeloma, anti–SARS-CoV-2 spike IgG titers and neutralizing activity were measured at 1 and 3 months from initial vaccination. Compared with healthy controls, patients with hematologic malignancy had attenuated antibody titers at 1 and 3 months. Furthermore, patients with hematologic malignancy had markedly diminished neutralizing capacity of 26.3% at 1 month and 43.6% at 3 months, despite positive seroconversion rates of 51.5% and 68.9% at the respective time points. Healthy controls had 93.2% and 100% neutralizing capacity at 1 and 3 months, respectively. Patients with leukemia, lymphoma, and multiple myeloma on observation had uniformly blunted responses. Treatment with Bruton tyrosine kinase inhibitors, venetoclax, phosphoinositide 3-kinase inhibitors, anti-CD19/CD20–directed therapies, and anti-CD38/B-cell maturation antigen–directed therapies substantially hindered responses, but single-agent immunomodulatory agents did not.Significance:Patients with hematologic malignancy have compromised COVID-19 vaccine responses at baseline that are further suppressed by active therapy, with many patients having insufficient neutralizing capacity despite positive antibody titers. Refining vaccine response parameters is critical to guiding clinical care, including the indication for booster vaccines, for this vulnerable population.See related article by Tamari et al., p. 577.This article is highlighted in the In This Issue feature, p. 549

We previously described clinically relevant reductions in fecal microbiota diversity in patients undergoing allogeneic hematopoietic cell transplantation (allo-HCT). Recipients of high-dose chemotherapy and autologous HCT (auto-HCT) incur similar antibiotic exposures and nutritional alterations. To characterize the fecal microbiota in the auto-HCT population, we analyzed 1161 fecal samples collected from 534 adult recipients of auto-HCT for lymphoma, myeloma, and amyloidosis in an observational study conducted at 2 transplantation centers in the United States. By using 16S ribosomal gene sequencing, we assessed fecal microbiota composition and diversity, as measured by the inverse Simpson index. At both centers, the diversity of early pretransplant fecal microbiota was lower in patients than in healthy controls and decreased further during the course of transplantation. Loss of diversity and domination by specific bacterial taxa occurred during auto-HCT in patterns similar to those with allo-HCT. Above-median fecal intestinal diversity in the periengraftment period was associated with decreased risk of death or progression (progression-free survival hazard ratio, 0.46; 95% confidence interval, 0.26-0.82; P = .008), adjusting for disease and disease status. This suggests that further investigation into the health of the intestinal microbiota in auto-HCT patients and posttransplant outcomes should be undertaken.

Dysgeusia is a common but understudied complication in patients undergoing autologous hematopoietic cell transplantation (auto-HCT). We assessed the feasibility of using chemical gustometry (CG) to measure dysgeusia and explored its associations with symptom burden, nutrition, chemotherapy pharmacokinetics (PK), and the oral microbiome.We conducted a single-center, prospective feasibility study (NCT03276481) of patients with multiple myeloma undergoing auto-HCT. CG was performed longitudinally testing five flavors (sweet, sour, salty, bitter, umami) to calculate a total taste score (maximum score, 30). We measured caloric intake and patient-reported symptoms, assessing their correlation with oral microbiota composition and salivary and blood melphalan PK exposure.Among all 45 patients, 39 (87%) completed at least four (60%) and 22 (49%) completed all six CG assessments. Median total CG scores remained stable over time but were lowest at day +7 (27, range 24-30) with recovery by day +100. Symptom burden was highest by day +10 (area under the curve, 2.9; range, 1.0-4.6) corresponding with the lowest median overall caloric intake (1624 kcal; range, 1345-2267). Higher serum/salivary melphalan levels correlated with higher patient-reported dysgeusia and lower caloric intake. Oral microbiota α-diversity was stable early and increased slightly by day +100.Assessment of dysgeusia by CG is feasible after auto-HCT. Most dysgeusia, symptom burden, and lowest caloric intake occurred during the blood count nadir. Higher melphalan concentrations correlated with more dysgeusia and poorer caloric intake. Future studies will aim to modulate melphalan exposure by PK-targeted dosing and characterize patient taste preferences to personalize diets for improved nutritional intake.Taste changes after cancer treatments are very common. We used chemical gustometry (taste testing) to study taste changes and to better understand why patients with multiple myeloma experience this symptom after autologous hematopoietic cell transplantation. We found that taste testing was feasible, taste changes peaked when blood counts were lowest, and most patients recovered their taste by 100 days after transplantation. Taste changes correlated with lower food intake and with higher levels of chemotherapy in the body. Future work will focus on using personalized chemotherapy doses to reduce taste changes and to match patients' individual taste preferences with their diets.

Purpose: Minimal residual disease (MRD) negativity is a strong predictor for outcome in multiple myeloma. To assess V(D)J clonotype capture using the updated Adaptive next-generation sequencing (NGS) MRD assay in a clinical setting, we analyzed baseline and follow-up samples from patients with multiple myeloma who achieved deep clinical responses. Experimental Design: A total of 159 baseline and 31 follow-up samples from patients with multiple myeloma were sequenced using the NGS MRD assay. Baseline samples were also sequenced using a targeted multiple myeloma panel (myTYPE). We estimated ORs with 95% confidence intervals (CI) for clonotypes detection using logistic regression. Results: The V(D)J clonotype capture rate was 93% in baseline samples with detectable genomic aberrations, indicating presence of tumor DNA, assessed through myTYPE. myTYPE-positive samples had significantly higher V(D)J clonotype detection rates in univariate (OR, 7.3; 95% CI, 2.8–22.6) and multivariate analysis (OR, 4.4; 95% CI, 1.4–16.9; P = 0.016). Higher disease burden was associated with higher probability of V(D)J clonotype capture, meanwhile no such association was found for age, gender, or type of heavy or light immunoglobulin chain. All V(D)J clonotypes detected at baseline were detected in MRD-positive samples indicating that the V(D)J clonotypes remained stable and did not undergo further rearrangements during follow-up. Of the 31 posttreatment samples, 12 were MRD-negative using the NGS MRD assay. Conclusions: NGS for V(D)J rearrangements in multiple myeloma offers a reliable and sensitive method for MRD tracking with high detection rates in the clinical setting.

Allogeneic hematopoietic cell transplantation (alloHCT) for multiple myeloma (MM), with its underlying graft-versus-tumor capacity, is a potentially curative approach for high-risk patients. Relapse is the main cause of treatment failure, but predictors for postrelapse survival are not well characterized. We conducted a retrospective analysis to evaluate predictors for postrelapse overall survival (OS) in 60 MM patients who progressed after myeloablative T cell-depleted alloHCT. The median patient age was 56 years, and 82% had high-risk cytogenetics. Patients received a median of 4 lines of therapy pre-HCT, and 88% achieved at least a partial response (PR) before alloHCT. Of the 38% who received preemptive post-HCT therapy, 13 received donor lymphocyte infusions (DLIs) and 10 received other interventions. Relapse was defined as very early ( 24 months; 22%). At relapse, 27% presented with extramedullary disease (EMD). The median postrelapse overall survival (OS) by time to relapse was 4 months for the very early relapse group, 17 months for the early relapse group, and 72 months for the late relapse group (P = .002). Older age, relapse with EMD

Introduction: Multiple myeloma (MM), a clonal disorder of terminally differentiated plasma cells, is the second most common hematologic malignancy with ~57.9% 5-year survival rate. Current MM therapies are not curative and in most patients MM relapse. Aiming to restore antitumor immunity and counteract MM evolution, we have developed a personalized dendritic(DC)/MM cell fusion vaccine, whereby several tumor antigens are presented in the context of DC mediated co-stimulation. BMT CTN 1401 is a multicenter randomized phase II clinical trial (NCT02728102) evaluating the efficacy of the DC/MM vaccine combined with lenalidomide maintenance (Len) after autoHCT. 203 patients were enrolled from 18 centers. Aim: To evaluate the impact of the DC/MM vaccine on the establishment of anti-MM immune response we profiled the peripheral blood (PB) immune landscape at the single-cell level, with particular focus on the T cell compartment. Method: We performed single-cell immunoprofiling (gene expression + V(D)J sequencing) on 40 patients (3xDC/MM vaccine/Len/GM-CSF: N=20; Len/GM-CSF: N=10; Len: N=10). 160 PB mononuclear cells (PBMC) samples were collected at enrollment, prior to Len, after 1 and 3 vaccines and were processed using the 10x Genomics single cell 5' assay. Here we present the analysis relative to 52 PBMC samples from 13 vaccinated patients included in the initial study cohort. The remaining 108 PBMC samples have already been subjected to single-cell immunoprofiling and the analysis is ongoing. Results: 309,423 cells passed quality-check identifying 47 cell populations, corresponding to 20 major compartments. The T cell compartment (146,373 cells) was divided into 14 different cell populations including activated CD8, CD4, and NKT cells that exhibited a gradual increase during the course of the study. Relatively, TCR sequencing demonstrated a recovery of T cell clonal diversity and a progressive rise in the frequency of expanded clonotypes within the activated CD4 and cytotoxic T cell populations after vaccination. Consistently, we observed a progressively raised number of shared TCR clonotypes within the activated CD8 and CD4 T cell subsets. The identification of common epitope/paratope hotspots among the expanded clonotypes and the different patients revealed a higher proportion of shared TCR clonotype groups across patients after vaccination compared to the early post-transplant period, predominantly after 3 vaccinations. Conclusions: Assessment of PBMC samples from 13 vaccinated patients provided a detailed picture of the PBMC landscape. The constant T cell expansion in patients following vaccination coupled with the shared paratope/epitope hotspots and TCR signatures among patients indicated the TCR cross-reactivity and suggested for the establishment of an anti-MM immune response. Citation Format: Giulia Cheloni, Dimitra Karagkouni, Daniela Torres, David J. Chung, Nina Shah, Natalie S. Callander, Thinle Chodon, Yvonne Efebera, Nancy Geller, Peiman Hematti, Hillard Lazarus, Ehsan Malek, Philip L. McCarthy, Ajay K. Nooka, Jacalyn Rosenblatt, Aaron P. Rapoport, Robert J. Soiffer, Dina Stroopinsky, Edmund K. Waller, Marcelo C. Pasquini, Ioannis Vlachos, David Avigan. Dendritic cell/myeloma fusion vaccine with lenalidomide maintenance following autologous hematopoietic cell transplant induced T cell activation and expansion [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6785.

Cellular therapies including allogeneic hematopoietic cell transplant (allo-HCT) and autologous hematopoietic cell transplant (auto-HCT) and chimeric antigen receptor (CAR) T-cell therapy render patients severely immunocompromised for extended periods after therapy, and data on responses to COVID-19 vaccines are limited. We analyzed anti–SARS-CoV-2 spike IgG Ab (spike Ab) titers and neutralizing Ab among 217 recipients of cellular treatments (allo-HCT, n = 149; auto-HCT, n = 61; CAR T-cell therapy, n = 7). At 3 months after vaccination, 188 patients (87%) had positive spike Ab levels and 139 (77%) had positive neutralization activity compared with 100% for both in 54 concurrent healthy controls. Time from cellular therapy to vaccination and immune recovery post–cellular therapy were associated with response. Vaccination against COVID-19 is an important component of post–cellular therapy care, and predictors of quantitative and qualitative response are critical in informing clinical decisions about optimal timing of vaccines and the requirement for booster doses. Significance: Identifying predictors of response to vaccination against SARS-CoV-2 in patients following cellular therapy is critical to managing this highly vulnerable patient population. To date, this is the most comprehensive study evaluating quantitative and qualitative responses to vaccination, providing parameters most predictive of response and potentially informing booster vaccination strategies. See related article by Chung et al., p. 568. This article is highlighted in the In This Issue feature, p. 549