Idecabtagene Vicleucel in Relapsed and Refractory Multiple Myeloma.

BACKGROUND: Idecabtagene vicleucel (ide-cel, also called bb2121), a B-cell maturation antigen-directed chimeric antigen receptor (CAR) T-cell therapy, has shown clinical activity with expected CAR T-cell toxic effects in patients with relapsed and refractory multiple myeloma. METHODS: In this phase 2 study, we sought to confirm the efficacy and safety of ide-cel in patients with relapsed and refractory myeloma. Patients with disease after at least three previous regimens including a proteasome inhibitor, an immunomodulatory agent, and an anti-CD38 antibody were enrolled. Patients received ide-cel target doses of 150 × 106 to 450 × 106 CAR-positive (CAR+) T cells. The primary end point was an overall response (partial response or better); a key secondary end point was a complete response or better (comprising complete and stringent complete responses). RESULTS: Of 140 patients enrolled, 128 received ide-cel. At a median follow-up of 13.3 months, 94 of 128 patients (73%) had a response, and 42 of 128 (33%) had a complete response or better. Minimal residual disease (MRD)-negative status (<10-5 nucleated cells) was confirmed in 33 patients, representing 26% of all 128 patients who were treated and 79% of the 42 patients who had a complete response or better. The median progression-free survival was 8.8 months (95% confidence interval, 5.6 to 11.6). Common toxic effects among the 128 treated patients included neutropenia in 117 patients (91%), anemia in 89 (70%), and thrombocytopenia in 81 (63%). Cytokine release syndrome was reported in 107 patients (84%), including 7 (5%) who had events of grade 3 or higher. Neurotoxic effects developed in 23 patients (18%) and were of grade 3 in 4 patients (3%); no neurotoxic effects higher than grade 3 occurred. Cellular kinetic analysis confirmed CAR+ T cells in 29 of 49 patients (59%) at 6 months and 4 of 11 patients (36%) at 12 months after infusion. CONCLUSIONS: Ide-cel induced responses in a majority of heavily pretreated patients with refractory and relapsed myeloma; MRD-negative status was achieved in 26% of treated patients. Almost all patients had grade 3 or 4 toxic effects, most commonly hematologic toxic effects and cytokine release syndrome. (Funded by bluebird bio and Celgene, a Bristol-Myers Squibb company; KarMMa ClinicalTrials.gov number, NCT03361748.).

Post-infusion Costs Associated with Idecabtagene Vicleucel Treatment for Patients with Relapsed/Refractory Multiple Myeloma in the KarMMa Trial.

INTRODUCTION: Patients with triple-class exposed relapsed/refractory multiple myeloma (RRMM) have poor outcomes with substantial healthcare costs. Idecabtagene vicleucel (ide-cel), a B-cell maturation antigen (BCMA)-directed chimeric antigen receptor (CAR) T cell therapy, showed deep, durable responses in patients with RRMM in the pivotal phase 2 KarMMa trial (NCT03361748). Healthcare resource utilization (HCRU) and costs were estimated for ide-cel-treated patients in the KarMMa trial. METHODS: Post-infusion costs were estimated based on HCRU data, including facility care, diagnostics, medications, and procedures. Length of stay (LOS) was extracted for inpatient and intensive care unit (ICU) care. All patients had a 14-day post-infusion inpatient stay per trial protocol. Analyses were conducted for patients treated in the United States (US), who received the ide-cel target dose of 450 × 106 CAR + T cells and assuming a 7-day inpatient stay. RESULTS: Overall, 128 patients received ide-cel and were included in this analysis. Mean age was 60 years, 59% were men, and 81% were white. Mean total LOS was 23.9 days. Total estimated costs over 24 months post-infusion were US$115,614 per patient, driven by facility costs (75%; $86,385). Most costs were incurred in the first month (58%; $67,259). The scenario analysis assuming a 7-day inpatient stay showed estimated 24-month costs of $92,294. For the 54 (42%) patients who received ide-cel high dose, total costs over 24 months were $113,298 per patient. CONCLUSIONS: Extrapolation of costs based on HCRU data from patients receiving single-infusion of ide-cel in the KarMMa trial showed substantially reduced HCRU and costs over 2 years after initial treatment. Most costs were incurred during the first month after ide-cel infusion, likely attributable to the 14-day inpatient stay required by the trial protocol. These findings suggest a nominal, incremental monthly cost of care immediately after treatment, which may be lower in routine clinical practice.

Characterizing the exposure-response relationship of idecabtagene vicleucel in patients with relapsed/refractory multiple myeloma.

Idecabtagene vicleucel (ide-cel; bb2121) is a B-cell maturation antigen-directed chimeric antigen receptor (CAR) T cell therapy approved for treatment of patients with heavily pretreated relapsed and refractory multiple myeloma. This analysis evaluated exposure-response (ER) relationships of ide-cel with key efficacy end points and safety events. Ide-cel exposure data were available from 127 patients treated at target doses of 150, 300, or 450 × 106 CAR+ T cells from the phase II KarMMa study (NCT03361748). Key exposure metrics, including area under the curve of the transgene level from 0 to 28 days and maximum transgene level, were calculated using noncompartmental methods. Logistic regression models, using both linear and maximum response function of exposure on the logit scale, were evaluated to quantify observed ER trends, and modified by including statistically significant individual covariates in a stepwise regression analysis. There was wide overlap of exposures across the target doses. ER relationships were observed for the overall and complete response rates, with higher response rates associated with higher exposures. Model-based evaluations identified female sex and baseline serum monoclonal protein less than or equal to 10 g/L as predictive of a higher objective response rate and a higher complete response rate, respectively. ER relationships were observed for safety events of cytokine release syndrome requiring tocilizumab or corticosteroids. The established ER models were used to quantify the ide-cel dose-response, which showed a positive benefit-risk assessment for the range of ide-cel exposures associated with the target dose range of 150-450 × 106 CAR+ T cells.

Analysis of patient-reported experiences up to 2 years after receiving idecabtagene vicleucel (ide-cel, bb2121) for relapsed or refractory multiple myeloma: Longitudinal findings from the phase 2 KarMMa trial.

OBJECTIVE: To understand the long-term experience of patients receiving ide-cel chimeric antigen receptor T (CAR T) cell therapy for relapsed or refractory multiple myeloma in the pivotal phase 2 KarMMa trial. METHODS: This qualitative study analyzed semi-structured patient interviews 6-24 months after ide-cel infusion. Thematic analysis with quantitative and longitudinal analyses explored patient perceptions of ide-cel treatment experience, advantages and disadvantages, and long-term health-related quality of life impact. Patient journeys were developed from narrative analysis of perceived treatment benefits with known remission length. RESULTS: Interviews with 45 patients 6-24 months postinfusion were analyzed; all reported ≥ 1 ide-cel treatment advantage, most often related to efficacy (n = 42/45, 93%), few or no side effects (n = 35/45, 78%), and avoidance of other treatments (n = 34/45, 76%). Patients generally reported 6-month improvements in physical health, functioning, emotional well-being, social life, and outlook on the future; these improvements mostly remained "stable" through 18 and 24 months. The most common patient journeys comprised physical, functioning, or emotional benefit with remission < 2 years. CONCLUSIONS: Longitudinal analysis of patient experiences showed sustained benefits and preference for ide-cel up to 24 months after treatment. Trial Registration Number and Date: NCT03361748. December 5, 2017.

Idecabtagene vicleucel for relapsed and refractory multiple myeloma: post hoc 18-month follow-up of a phase 1 trial.

Idecabtagene vicleucel (ide-cel) is a B-cell-maturation antigen (BCMA)-directed chimeric antigen receptor T cell therapy. We performed a post hoc analysis of a single-arm phase 1 multicenter study in relapsed/refractory multiple myeloma (CRB-401) (n = 62; median follow-up, 18.1 months). The primary endpoint was safety outcomes, and secondary endpoints included overall response rate (ORR), complete response (CR) and very good partial response (VGPR). The study met its primary endpoint with low rates of grade 3/grade 4 cytokine release syndrome (6.5%) and neurotoxicity (1.6%). ORR was 75.8%; 64.5% achieved VGPR or better and 38.7% achieved CR or stringent CR. Among exploratory endpoints, median duration of response, progression-free survival (PFS) and overall survival were 10.3, 8.8 and 34.2 months, respectively, and ide-cel expansion in blood and bone marrow correlated with clinical efficacy and postinfusion reduction of soluble BCMA. Patients with PFS ≥ 18 months had more naive and less exhausted T cells in apheresis material and improved functional T cell phenotype in the drug product compared with those with less durable responses. These results confirm ide-cel safety, tolerability and efficacy and describe T cell qualities that correlate with durable response. Clinicaltrials.gov identifier : NCT02658929 .

Health-related quality of life with idecabtagene vicleucel in relapsed and refractory multiple myeloma.

Idecabtagene vicleucel (ide-cel), a B-cell maturation antigen-directed chimeric antigen receptor T cell therapy, showed deep, durable responses in patients with triple-class exposed, relapsed and refractory multiple myeloma (RRMM) in the phase 2 KarMMa (Efficacy and Safety Study of bb2121 in Subjects With Relapsed and Refractory Multiple Myeloma) trial. We assessed health-related quality of life (HRQoL) among KarMMa patients. The European Organization for Research and Treatment of Cancer Quality of Life C30 Questionnaire and its supplementary 20-item multiple myeloma module, as well as the EuroQol 5-dimension 5-level instrument, were administered at screening, baseline (≤72 hours before or same day as lymphodepletion), day of ide-cel treatment, and after ide-cel treatment. Mean changes from baseline that exceeded the predetermined threshold of minimally important difference were deemed clinically meaningful. The proportions of patients experiencing clinically meaningful changes in HRQoL were assessed using within-patient change thresholds. Time to stable improvement (≥2 consecutive visits with clinically meaningful HRQoL improvements) was analyzed by using the Kaplan-Meier method. A total of 126 (98%) of 128 patients treated with ide-cel were included in the HRQoL analysis. Pretreatment baseline RRMM burden was high and meaningfully worse than that in the age- and sex-weighted general population. Statistically significant and clinically meaningful improvements from baseline were observed by month 1 for pain (-8.9) and disease symptoms (-10.2), and by month 2 for fatigue (-7.2), physical functioning (6.1), cognitive functioning (6.7), and global health status/QoL (8.0). Clinically meaningful improvements in fatigue, pain, and physical functioning were most prominent at months 9, 12, and 18, respectively, and were sustained through 15 to 18 months after ide-cel treatment. For triple-class exposed patients with RRMM with a poor prognosis and few treatment options, a single ide-cel infusion provides early, sustained, statistically significant, and clinically meaningful improvements in HRQoL. This study was registered at Clinicaltrials.gov as #NCT03361748.

Patient experience before and after treatment with idecabtagene vicleucel (ide-cel, bb2121): qualitative analysis of patient interviews in the KarMMa trial.

OBJECTIVE: To understand the experience of patients with relapsed and refractory multiple myeloma (RRMM) receiving idecabtagene vicleucel (ide-cel), a B-cell maturation antigen-directed chimeric antigen receptor T cell therapy, in the pivotal, phase 2 KarMMa trial. METHODS: Optional semi-structured interviews before leukapheresis (pre-treatment) captured expectations and after ide-cel infusion (1, 2, and 3 months post-treatment), assessed treatment experience, ide-cel advantages/disadvantages, and health and well-being. In a mixed-method analysis, treatment experiences were categorized by clinical response status, health and well-being, and self-reported recovery after infusion. RESULTS: Pre-treatment interviews indicated unmet treatment needs. In post-treatment interviews, most patients reported the positives of ide-cel outweighed negatives (69%, n = 27/39). Most common advantages of ide-cel were efficacy (18-64%), favorable side-effect profile (46-68%), and recovery time (13-18%); most common disadvantages were related to side effects (13-20%). When analyzed by clinical response, patients most often had stringent complete or very good partial response and improved health and well-being with mild or severe recovery from the infusion (27/58, 47%). Most patients with minimal clinical response reported mild infusion recovery (5/6, 83%). CONCLUSIONS: Patient interviews before ide-cel treatment showed unmet needs in triple-class exposed RRMM. Post-treatment experiences generally favored ide-cel versus previously received treatments.

Rapid mobilization of murine and human hematopoietic stem and progenitor cells with AMD3100, a CXCR4 antagonist.

Improving approaches for hematopoietic stem cell (HSC) and hematopoietic progenitor cell (HPC) mobilization is clinically important because increased numbers of these cells are needed for enhanced transplantation. Chemokine stromal cell derived factor-1 (also known as CXCL12) is believed to be involved in retention of HSCs and HPCs in bone marrow. AMD3100, a selective antagonist of CXCL12 that binds to its receptor, CXCR4, was evaluated in murine and human systems for mobilizing capacity, alone and in combination with granulocyte colony-stimulating factor (G-CSF). AMD3100 induced rapid mobilization of mouse and human HPCs and synergistically augmented G-CSF-induced mobilization of HPCs. AMD3100 also mobilized murine long-term repopulating (LTR) cells that engrafted primary and secondary lethally-irradiated mice, and human CD34(+) cells that can repopulate nonobese diabetic-severe combined immunodeficiency (SCID) mice. AMD3100 synergized with G-CSF to mobilize murine LTR cells and human SCID repopulating cells (SRCs). Human CD34(+) cells isolated after treatment with G-CSF plus AMD3100 expressed a phenotype that was characteristic of highly engrafting mouse HSCs. Synergy of AMD3100 and G-CSF in mobilization was due to enhanced numbers and perhaps other characteristics of the mobilized cells. These results support the hypothesis that the CXCL12-CXCR4 axis is involved in marrow retention of HSCs and HPCs, and demonstrate the clinical potential of AMD3100 for HSC mobilization.

Ex vivo rapamycin treatment of human cord blood CD34+ cells enhances their engraftment of NSG mice.

Since cord blood (CB) has become a commonly used source of transplantable hematopoietic stem (HSC) and hematopoietic progenitor cells (HPC), there has been a need to overcome the limited HSC and HPC numbers available to transplant from a single CB, especially for adult recipients. Our laboratory previously demonstrated that Rheb2 overexpression significantly impaired the repopulating ability of HSC. Since overexpression of Rheb2 leads to increased signaling through mTOR, we examined the effect of the mTOR inhibitor rapamycin ex vivo on cytokine expanded CD34(+) CB cells for the engraftment of these cells in non-obese diabetic, severe combined immunodeficient, IL-2 receptor γ chain null (NSG) mice. We observed significant enhancement in engraftment of the CB treated ex vivo with cytokines in the presence of rapamycin prior to transplant, effects seen in primary as well as secondary transplants. These pre-clinical results suggest a positive role for rapamycin during ex vivo culture of CB SCID repopulating cells/HSC.

Overexpression of Rheb2 enhances mouse hematopoietic progenitor cell growth while impairing stem cell repopulation.

Molecular mechanisms preserving hematopoietic stem cell (HSC) self-renewal by maintaining a balance between proliferation, differentiation, and other processes are not fully understood. Hyperactivation of the mammalian target of rapamycin (mTOR) pathway, causing sustained proliferative signals, can lead to exhaustion of HSC repopulating ability. We examined the role of the novel ras gene Rheb2, an activator of the mTOR kinase, in colony-forming ability, survival, and repopulation of immature mouse hematopoietic cells. In a cell line model of mouse hematopoietic progenitor cells (HPCs), we found enhanced proliferation and mTOR signaling in cells overexpressing Rheb2. In addition, overexpression of Rheb2 enhanced colony-forming ability and survival of primary mouse bone marrow HPCs. Expansion of phenotypic HSCs in vitro was enhanced by Rheb2 overexpression. Consistent with these findings, Rheb2 overexpression transiently expanded phenotypically defined immature hematopoietic cells after in vivo transplantation; however, these Rheb2-transduced cells were significantly impaired in overall repopulation of primary and secondary congenic transplantation recipients. Our findings suggest that HPCs and HSCs behave differently in response to growth-promoting signals stimulated by Rheb2. These results may have value in elucidating mechanisms controlling the balance between proliferation and repopulating ability, a finding of importance in clinical uses of HPCs/HSCs.

Effective anti-BCMA retreatment in multiple myeloma.

The recent emergence of anti-B-cell maturation antigen (BCMA) therapies holds great promise in multiple myeloma (MM). These include chimeric antigen receptor (CAR) T cells, bispecific antibodies, and antibody-drug conjugates. Their development in clinical trials and further approval are changing the strategy for treating MM. Considering that a cure has not been reached, a central question in the coming years will be the possibility of using these therapies sequentially. Here, we report 2 cases of the serial use of anti-BCMA therapies with parallel monitoring of BCMA expression and anti-CAR antibodies. We further discuss recent data from clinical studies that have informed us about the different mechanisms of resistance to anti-BCMA therapies, including antigen escape, BCMA shedding, anti-drug antibodies, T-cell exhaustion, and the emergence of an immunosuppressive microenvironment. This knowledge will be essential to help guide the strategy of serial treatments with anti-BCMA therapies.

Identification of parameters required for efficient lentiviral vector transduction and engraftment of human cord blood CD34(+) NOD/SCID-repopulating cells.

OBJECTIVE: Human cord blood (CB) is a potential source of hematopoietic stem cells (HSC) for gene therapy to treat patients with hematopoietic disorders. However, limited numbers of CB CD34(+) cells, low transduction efficiency with lentiviral vectors (LVs), and low engraftment efficiency of nonobese diabetic/severe combined immunodeficient (NOD/SCID) repopulating cells (SRC), a measure of HSC, are blocks to this procedure. To optimize culture and transduction conditions, we compared various lengths of time for prestimulation before transduction, transduction duration, and posttransduction cell culture. MATERIALS AND METHODS: We used a LV to transduce human CB CD34(+) cells followed by engraftment into NOD/SCID mice. We evaluated the effects of prestimulation and transduction time and optimized ex vivo cell culture duration before transplantation. RESULTS: We were able to achieve up to 40% transduction efficiency and up to 50% engraftment efficiency of SRC in CB CD34(+) cells when CB CD34(+) cells were either not prestimulated or prestimulated in 1% fetal bovine serum medium for 1 hour, followed by 5 hours transduction and 3 days culture in a cocktail of growth factors after transduction. No apparent functional changes of CB CD34(+) cells were noted under these conditions. CONCLUSION: This gene-transduction/cell-expansion protocol is the first systematic study to optimize prestimulation time, transduction time, and, very importantly, ex vivo culture time after transduction, and may be of use for LV gene transduction in a gene therapy setting.

CD26 inhibition and hematopoiesis: a novel approach to enhance transplantation.

Dipeptidylpeptidase IV/CD26 is expressed on the surface of various cell types. Through its enzymatic activity, its major function is to cleave the N-terminal dipeptide from diverse molecules including members of the chemokine family of cytokines. The N-terminus of these chemokines is important for activation of and binding to seven-transmembrane G-protein linked chemokine receptors, and early studies showed truncation by CD26 physiologically alters these properties of select chemokines resulting in diverse functional outcomes. Stromal-derived factor-1 (SDF-1/CXCL12), a chemokine involved in hematopoietic cell chemotaxis, homing, mobilization and survival, is cleaved by CD26 producing a form that is inactive in CXCR4 signaling and has some antagonistic properties in vitro. Recent studies have shown that the inhibition of cell-surface CD26 peptidase activity on hematopoietic stem/progenitor cell (HSC/HPC) populations increases their SDF-1/CXCL12 directed chemotaxis in vitro, and in vivo homing and engraftment. CD26 inhibition may, therefore, represent a novel approach to increasing the efficacy and success of HSC/HPC transplantation, especially under conditions of limiting donor cell yield.

Inhibition of CD26 in human cord blood CD34+ cells enhances their engraftment of nonobese diabetic/severe combined immunodeficiency mice.

CD26, a surface serine dipeptidylpeptidase IV (DPPIV) expressed on different cell types, cleaves the amino-terminal dipeptide from some chemokines, including stromal-derived factor-1 (SDF-1/CXCL12). SDF-1/CXCL12 plays important roles in hematopoietic stem cell (HSC) homing, engraftment, and mobilization. Inhibition of CD26 peptidase activity enhances homing, engraftment, and competitive repopulation in congenic mouse bone marrow cell transplants. Our studies evaluated a role for CD26 in in vivo engraftment of HSCs from human umbilical cord blood (CB) into nonobese diabetic/severe combined immunodeficiency (NOD/SCID) mice. Pretreating purified CD34(+) human CB cells with Diprotin A, a DPPIV inhibitor, for 15 min significantly enhanced engraftment. Treatment did not affect differentiation of CD34(+) cells in vivo, as measured phenotypically by human markers CD33, CD38, CD19, and CD34. We found that the percentage of CD26(+) cells within the more immature cells (CD34(+)CD38()) was significantly higher than in the more mature population (CD34(+)CD38(+)). These results suggest that inhibition of CD26 may be one way to enhance engraftment of limiting numbers of stem cells during CB transplantation.

MRI findings in pediatric ophthalmoplegic migraine: a case report and literature review.

Ophthalmoplegic migraine (also recognized as a cranial neuralgia) is a form of migraine characterized by recurrent episodes of headache with ophthalmoplegia related to paresis of cranial nerves III, IV, or VI, with onset typically in childhood. These symptomatic episodes may persist for several hours or for several weeks, months, or permanently. To date, the exact etiology of ophthalmoplegic migraine remains unknown. In previous case reports, ophthalmoplegic migraine may or may not be associated with changes seen on magnetic resonance imaging. Contrast-enhanced magnetic resonance imaging performed during symptomatic and postsymptomatic periods in patients with ophthalmoplegic migraine may hold great value in identifying the pathophysiologic features of oculomotor nerve palsies. Of cases demonstrating abnormal magnetic resonance imaging, a majority show improved but persistent changes on repeat imaging. The present report describes a case of recurrent ophthalmoplegic migraine in a 16-year-old girl. Although the patient presented with ophthalmoplegic migraine during this episode in the same manner as her prior episodes, enhancement of the cranial nerve III on magnetic resonance imaging was evident during the eighth episode whereas previous imaging had been normal. Complete resolution of enhancement of the oculomotor nerve on repeat imaging adds to the few cases that have shown such findings in patients with recurrent ophthalmoplegic migraine. A review of previous reported cases of ophthalmoplegic migraine is offered.

Modulation of Hematopoietic Chemokine Effects In Vitro and In Vivo by DPP-4/CD26.

Dipeptidyl peptidase 4 (DPP4)/CD26 truncates certain proteins, and this posttranslational modification can influence their activity. Truncated (T) colony-stimulating factors (CSFs) are decreased in potency for stimulating proliferation of hematopoietic progenitor cells (HPCs). T-CXCL12, a modified chemokine, is inactive as an HPC chemotactic, survival, and enhancing factor for replating or ex-vivo expansion of HPCs. Moreover, T-CSFs and T-CXCL12 specifically downmodulates the positively acting effects of their own full-length molecule. Other chemokines have DPP4 truncation sites. In the present study, we evaluated effects of DPP4 inhibition (by Diprotin A) or gene deletion of HPC on chemokine inhibition of multicytokine-stimulated HPC, and on chemokine-enhancing effects on single CSF-stimulated HPC proliferation, as well as effects of DPP4 treatment of a number of chemokines. Myelosuppressive effects of chemokines with, but not without, a DPP4 truncation site were greatly enhanced in inhibitory potency by pretreating target bone marrow (BM) cells with Diprotin A, or by assaying their activity on dpp4/cd26(-/-) BM cells. DPP4 treatment of myelosuppressive chemokines containing a DPP4 truncation site produced a nonmyelosuppressive molecule, but one which had the capacity to block suppression by that unmodified chemokine both in vitro and in vivo. Additionally, DPP4 treatment ablated the single cytokine-stimulated HPC-enhancing activity of CCL3/MIP-1α and CCL4/MIP-1ß, and blocked the enhancing activity of each unmodified molecule, in vitro and in vivo. These results highlight the functional posttranslational modulating effects of DPP4 on chemokine activities, and information offering additional biological insight into chemokine regulation of hematopoiesis.

Normal and leukemic stem cell niches: insights and therapeutic opportunities.

Hematopoietic stem cells (HSCs) rely on instructive cues from the bone marrow (BM) niche to maintain their quiescence and adapt blood production to the organism's needs. Alterations in the BM niche are commonly observed in blood malignancies and directly contribute to the aberrant function of disease-initiating leukemic stem cells (LSCs). Here, we review recent insights into the cellular and molecular determinants of the normal HSC niche and describe how genetic changes in stromal cells and leukemia-induced BM niche remodeling contribute to blood malignancies. Moreover, we discuss how these findings can be applied to non-cell-autonomous therapies targeting the LSC niche.

Dipeptidylpeptidase 4 negatively regulates colony-stimulating factor activity and stress hematopoiesis.

Enhancement of hematopoietic recovery after radiation, chemotherapy, or hematopoietic stem cell (HSC) transplantation is clinically relevant. Dipeptidylpeptidase (DPP4) cleaves a wide variety of substrates, including the chemokine stromal cell-derived factor-1 (SDF-1). In the course of experiments showing that inhibition of DPP4 enhances SDF-1-mediated progenitor cell survival, ex vivo cytokine expansion and replating frequency, we unexpectedly found that DPP4 has a more general role in regulating colony-stimulating factor (CSF) activity. DPP4 cleaved within the N-termini of the CSFs granulocyte-macrophage (GM)-CSF, G-CSF, interleukin-3 (IL-3) and erythropoietin and decreased their activity. Dpp4 knockout or DPP4 inhibition enhanced CSF activities both in vitro and in vivo. The reduced activity of DPP4-truncated versus full-length human GM-CSF was mechanistically linked to effects on receptor-binding affinity, induction of GM-CSF receptor oligomerization and signaling capacity. Hematopoiesis in mice after radiation or chemotherapy was enhanced in Dpp4(-/-) mice or mice receiving an orally active DPP4 inhibitor. DPP4 inhibition enhanced engraftment in mice without compromising HSC function, suggesting the potential clinical utility of this approach.

TGF-beta combined with M-CSF and IL-4 induces generation of immune inhibitory cord blood dendritic cells capable of enhancing cytokine-induced ex vivo expansion of myeloid progenitors.

Tolerogenic dendritic cells (DCs) may be valuable in transplantation for silencing immune reaction. Macrophage colony-stimulating factor (M-CSF)/IL-4 induces differentiation of cord blood (CB) monocytes into DCs (M-DCs) with tolerogenic phenotype/function. We assessed whether factors produced by tolerogenic DCs could modulate hematopoiesis. TGF-beta1 added to CB M-DC cultures induced bona fide DC morphology (TGF-M-DCs), similar to that of DCs generated with TGF-beta and granulocyte-macrophage colony-stimulating factor (GM-CSF)/IL-4 (TGF-GM-DCs). Of conditioned media (CM) produced from TGF-M-DCs, TGF-GM-DCs, M-DCs, and GM-DCs, TGF-M-DC CM was the only one that enhanced SCF, Flt3 ligand, and TPO expansion of myeloid progenitor cells ex vivo. This effect was blocked by neutralizing anti-M-CSF Ab, but protein analysis of CM suggested that M-CSF alone was not manifesting enhanced expansion of myeloid progenitors. LPS-stimulated TGF-M-DCs induced T-cell tolerance/anergy as effectively as M-DCs. TGF-M-DCs secreted significantly lower concentrations of progenitor cell inhibitory cytokines and were less potent in activating T cells than TGF-GM-DCs. Functional differences between TGF-M-DCs and TGF-GM-DCs included enhanced responses to LPS-induced ERK, JNK, and P38 activation in TGF-M-DCs and their immune suppressive-skewed cytokine release profiles. TGF-M-DCs appear unique among culture-generated DCs in their capability for silencing immunity while promoting expansion of myeloid progenitors, events that may be of therapeutic value.