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Hematotoxicity after chimeric antigen receptor (CAR) T-cell therapy is associated with infection and death but management remains unclear. We report results of 31 patients receiving hematopoietic stem cell boost (HSCB; 30 autologous, 1 allogeneic) for either sustained severe neutropenia of grade 4 (<0.5 × 109/L), sustained moderate neutropenia (≤1.5 × 109/L) and high risk of infection, or neutrophil count ≤2.0 × 109/L and active infection. Median time from CAR T-cell therapy to HSCB was 43 days and median absolute neutrophil count at time of HSCB was 0.2. Median duration of neutropenia before HSCB was 38 days (range, 7-151). Overall neutrophil response rate (recovery or improvement) was observed in 26 patients (84%) within a median of 9 days (95% confidence interval, 7-14). Time to response was significantly associated with the duration of prior neutropenia (P = .007). All nonresponders died within the first year after HSCB. One-year overall survival for all patients was 59% and significantly different for neutropenia (≤38 days; 85%) vs neutropenia >38 days before HSCB (44%; P = .029). In conclusion, early or prophylactic HSCB showed quick response and improved outcomes for sustained moderate to severe neutropenia after CAR-T.

•HSCBs for persistent neutropenia showed recovery or sustained neutrophil improvement in 84% of patients.•HSCBs given early and even for moderate neutropenia but high risk for infection showed excellent outcome.

Immunomodulatory drugs (IMiDs), such as thalidomide and its derivatives lenalidomide and pomalidomide, are key treatment modalities for hematologic malignancies, particularly multiple myeloma (MM) and del(5q) myelodysplastic syndrome (MDS). Cereblon (CRBN), a substrate receptor of the CRL4 ubiquitin ligase complex, is the primary target by which IMiDs mediate anticancer and teratogenic effects. Here we identify a ubiquitin-independent physiological chaperone-like function of CRBN that promotes maturation of the basigin (BSG; also known as CD147) and solute carrier family 16 member 1 (SLC16A1; also known as MCT1) proteins. This process allows for the formation and activation of the CD147–MCT1 transmembrane complex, which promotes various biological functions, including angiogenesis, proliferation, invasion and lactate export. We found that IMiDs outcompete CRBN for binding to CD147 and MCT1, leading to destabilization of the CD147–MCT1 complex. Accordingly, IMiD-sensitive MM cells lose CD147 and MCT1 expression after being exposed to IMiDs, whereas IMiD-resistant cells retain their expression. Furthermore, del(5q) MDS cells have elevated CD147 expression, which is attenuated after IMiD treatment. Finally, we show that BSG (CD147) knockdown phenocopies the teratogenic effects of thalidomide exposure in zebrafish. These findings provide a common mechanistic framework to explain both the teratogenic and pleiotropic antitumor effects of IMiDs.

The cytomegalovirus (CMV)-specific CD8+ cytotoxic T-lymphocyte (CTL) and CD4+ T-helper cell (Th) functions were characterized in 15 CMV seropositive recipients of autologous peripheral blood stem cell or bone marrow transplants. These immune functions were evaluated in peripheral blood specimens obtained before and at 1, 2, and 3 months after transplant. For study of CTL activity, blood mononuclear cells were cocultured with CMV-infected autologous fibroblasts for 2 weeks and then tested for cytotoxicity against CMV-infected or mock-infected autologous and HLA-mismatched fibroblasts. The Th response to CMV antigen was assessed by standard lymphoproliferative assay. CMV-specific CD8+ CTL and CD4+ Th responses were detectable in 12 (80%) and 14 (93%) patients, respectively, in the first 3 months after transplantation. A Th response to CMV was always present by the time of first CTL detection. During the posttransplant period, CMV infection occurred in 6 (40%) patients, and detection of CMV-specific CD8+ CTL activity was associated with protection from subsequent CMV infection (P = .002). Among CMV seropositive autograft recipients, CMV-specific CD8+ CTL and CD4+ Th responses are restored in a large proportion of patients in the first 3 months after transplantation, and the presence of a specific CD8+ CTL activity affords protection from CMV infection.

We have recently shown that Hsp90 is overexpressed in multiple myeloma (MM) and critically contributes to tumor cell survival. Pharmacologic blockade of Hsp90 has consistently been shown to induce MM cell death. However, most data have been obtained with MM cell lines whereas knowledge about the molecular effects of pharmacologic Hsp90 blockade in primary tumor cells is lacking. Furthermore, these investigations have so far exclusively relied on geldanamycin derivatives. Here, we analyzed the anti-tumor effects of a novel diarylisoxazole-based Hsp90 inhibitor (NVP-AUY922) in a large set of primary MM samples and in MM cell lines. The majority of cell lines (n = 8), as well as most primary samples (n = 20), displayed profound apoptotic responses and steep dose-effect curves with EC50 values in the range of 5–15 nM and EC90 values between 8 and 25 nM. This effect was not attenuated in coculture with cells from the bone marrow microenvironment. Some cell lines and about a quarter of primary MM samples displayed greater resilience to drug treatment, with EC50 values but not EC90 values reached at concentrations up to 50 nM. Sensitivity of MM cells to the Hsp90 inhibitor was not correlated with TP53 mutation or Hsp70 induction levels. Western analyses of MM cell lines and flow cytometric analyses of antibody-stained Hsp90 client proteins in primary tumor cells showed that NVP-AUY922-treatment entailed molecular effects and pharmacodynamic properties consistent with abrogation of Hsp90 function. Consequently, downregulation of multiple signaling and survival pathways was detectable through, for example, decreases in the phosphorylated (activated) forms of extracellular signal-regulated kinase (ERK) 1 and 2, signal transducer and activator of transcription (STAT) 3 and glycogen synthase kinase-3beta. All samples treated displayed strong upregulation of Hsp70. Importantly, peripheral blood mononuclear cells as well as primary bone marrow stromal cells were much less affected by high (50–100 nM) concentrations of NVP-AUY922, showing that a therapeutic window might be established for the treatment of multiple myeloma. Taken together, NVP-AUY922 could be a promising new drug for the treatment of a majority of myeloma patients.

This study was designed to determine the maximum-tolerated dose (MTD), dose-limiting toxicity (DLT), safety, and efficacy of intravenous cyclophosphamide (CY) in combination with the proteasome inhibitor bortezomib and high-dose dexamethasone (DEX) for remission induction in younger patients with newly diagnosed multiple myeloma (MM). Patients ≤ 60 years were enrolled to receive three 3-week treatment cycles with bortezomib 1.3 mg/m2/dose on days 1, 4, 8, and 11 in combination with DEX 40 mg/day orally on the day of bortezomib injection and the day thereafter. In addition, patients received CY intravenously on day 1 at either 600, 900, 1200, or 1500 mg/m2 - the optimal dose had to be defined. Recommended concomitant medication included bisphosphonates, antacids, prophylactic antiviral treatment, prophylaxis against pneumocystis pneumonia, and oral non-absorbable antifungal medication. In addition, antiemetics, cytokines, and intravenous immunoglobulins were allowed. DLT was defined using the National Cancer Institute common terminology criteria for adverse events, version 3.0 as grade 4 hematologic toxicity, ≥ grade 3 non-hematologic toxicity (except emesis, vomiting, and alopecia), ≥ grade 3 peripheral neuropathy, and ≥ grade 2 peripheral neuropathy with pain. MTD was defined as the highest dose studied for which the incidence of DLT was ≤ 33%. Thirty patients completed 78 treatment cycles. Twenty seven patients were evaluable for CY dose definition. Start dose level for CY was 1200 mg/m2. Since no patient experienced a DLT the dose level was increased to 1500 mg/m2. On this dose level a DLT occurred in 2/3 patients (67%). Therefore the dose level was decreased again to 1200 mg/m2 with 4/12 (33%) of patients experiencing DLT. On the next lower dose level a DLT was observed in 8% (1/12). Thus, the MTD for CY in combination with bortezomib and DEX based on cycle 1 was defined as 900mg/m2. Dose-limiting toxicities included leukopenia (n=5), neutropenia (n=1), and pneumonia (n=1). No patient died. Other adverse events not reaching dose-limiting intensity included thrombocytopenia, gastrointestinal irritations, fatigue, neuropathy and one patient with herpes zoster. Median time to best response was 63 days. The overall response rate (EBMT criteria) to up to three cycles of this combination was 87%, with 3 complete responses, 20 partial responses and 3 minor responses. No patient experienced progressive disease. Bortezomib combined with DEX and CY is a highly effective treatment for newly diagnosed MM. Recommended phase II/III dose of CY in this combination is 900 mg/m2. This schedule is currently being evaluated as pretransplant induction in newly diagnosed MM in a prospective trial of the Deutsche Studiengruppe Multiples Myelom (DSMM).

We have recently shown that Hsp90 is overexpressed in multiple myeloma (MM) and critically contributes to tumor cell survival. Pharmacologic blockade of Hsp90 has consistently been shown to induce MM cell death. However, most data have been obtained with MM cell lines whereas knowledge about the molecular effects of pharmacologic Hsp90 blockade in primary tumor cells is lacking. Furthermore, these investigations have so far exclusively relied on geldanamycin derivatives. Here, we analyzed the anti-tumor effects of a novel diarylisoxazole-based Hsp90 inhibitor (NVP-AUY922) in a large set of primary MM samples and in MM cell lines. The majority of cell lines (n = 8), as well as most primary samples (n = 20), displayed profound apoptotic responses and steep dose-effect curves with EC50 values in the range of 5–15 nM and EC90 values between 8 and 25 nM. This effect was not attenuated in coculture with cells from the bone marrow microenvironment. Some cell lines and about a quarter of primary MM samples displayed greater resilience to drug treatment, with EC50 values but not EC90 values reached at concentrations up to 50 nM. Sensitivity of MM cells to the Hsp90 inhibitor was not correlated with TP53 mutation or Hsp70 induction levels. Western analyses of MM cell lines and flow cytometric analyses of antibody-stained Hsp90 client proteins in primary tumor cells showed that NVP-AUY922-treatment entailed molecular effects and pharmacodynamic properties consistent with abrogation of Hsp90 function. Consequently, downregulation of multiple signaling and survival pathways was detectable through, for example, decreases in the phosphorylated (activated) forms of extracellular signal-regulated kinase (ERK) 1 and 2, signal transducer and activator of transcription (STAT) 3 and glycogen synthase kinase-3beta. All samples treated displayed strong upregulation of Hsp70. Importantly, peripheral blood mononuclear cells as well as primary bone marrow stromal cells were much less affected by high (50–100 nM) concentrations of NVP-AUY922, showing that a therapeutic window might be established for the treatment of multiple myeloma. Taken together, NVP-AUY922 could be a promising new drug for the treatment of a majority of myeloma patients.

This study was designed to determine the maximum-tolerated dose (MTD), dose-limiting toxicity (DLT), safety, and efficacy of intravenous cyclophosphamide (CY) in combination with the proteasome inhibitor bortezomib and high-dose dexamethasone (DEX) for remission induction in younger patients with newly diagnosed multiple myeloma (MM). Patients ≤ 60 years were enrolled to receive three 3-week treatment cycles with bortezomib 1.3 mg/m2/dose on days 1, 4, 8, and 11 in combination with DEX 40 mg/day orally on the day of bortezomib injection and the day thereafter. In addition, patients received CY intravenously on day 1 at either 600, 900, 1200, or 1500 mg/m2- the optimal dose had to be defined. Recommended concomitant medication included bisphosphonates, antacids, prophylactic antiviral treatment, prophylaxis against pneumocystis pneumonia, and oral non-absorbable antifungal medication. In addition, antiemetics, cytokines, and intravenous immunoglobulins were allowed. DLT was defined using the National Cancer Institute common terminology criteria for adverse events, version 3.0 as grade 4 hematologic toxicity, ≥ grade 3 non-hematologic toxicity (except emesis, vomiting, and alopecia), ≥ grade 3 peripheral neuropathy, and ≥ grade 2 peripheral neuropathy with pain. MTD was defined as the highest dose studied for which the incidence of DLT was ≤ 33%. Thirty patients completed 78 treatment cycles. Twenty seven patients were evaluable for CY dose definition. Start dose level for CY was 1200 mg/m2. Since no patient experienced a DLT the dose level was increased to 1500 mg/m2. On this dose level a DLT occurred in 2/3 patients (67%). Therefore the dose level was decreased again to 1200 mg/m2with 4/12 (33%) of patients experiencing DLT. On the next lower dose level a DLT was observed in 8% (1/12). Thus, the MTD for CY in combination with bortezomib and DEX based on cycle 1 was defined as 900mg/m2. Dose-limiting toxicities included leukopenia (n=5), neutropenia (n=1), and pneumonia (n=1). No patient died. Other adverse events not reaching dose-limiting intensity included thrombocytopenia, gastrointestinal irritations, fatigue, neuropathy and one patient with herpes zoster. Median time to best response was 63 days. The overall response rate (EBMT criteria) to up to three cycles of this combination was 87%, with 3 complete responses, 20 partial responses and 3 minor responses. No patient experienced progressive disease. Bortezomib combined with DEX and CY is a highly effective treatment for newly diagnosed MM. Recommended phase II/III dose of CY in this combination is 900 mg/m2. This schedule is currently being evaluated as pretransplant induction in newly diagnosed MM in a prospective trial of the Deutsche Studiengruppe Multiples Myelom (DSMM).

The combined blockade of the IL-6R/STAT3 and the MAPK signaling pathways has been shown to inhibit bone marrow microenvironment-mediated survival of multiple myeloma (MM) cells. Here, we identify the molecular chaperones heat shock protein (Hsp) 90alpha and beta as target genes of both pathways. Interestingly, in situ overexpression of both Hsp90 proteins was observed in the majority of MM, but not in MGUS or in normal plasma cells. SiRNA-mediated knockdown of Hsp90 or treatment with the novel Hsp90 inhibitor 17-DMAG attenuated the levels of phospho-STAT3 and phospho-ERK and decreased the viability of MM cells. Although knockdown of Hsp90beta unlike knockdown of Hsp90alpha was sufficient to induce apoptosis, this effect was strongly increased when both Hsp90s were targeted, indicating a cooperation of both. Given the importance of the bone marrow microenvironment for drug resistance and MM cell survival, apoptosis induced by Hsp90 inhibition was not mitigated in the presence of bone marrow stromal cells, osteoclasts or endothelial cells. These observations suggest, that a positive feedback loop consisting of Hsp90alpha/beta and major signaling pathways supports the survival of MM cells. Our results emphasize a role for Hsp90alpha and Hsp90beta in MM pathogenesis.

The combined blockade of the IL-6R/STAT3 and the MAPK signaling pathways has been shown to inhibit bone marrow microenvironment-mediated survival of multiple myeloma (MM) cells. Here, we identify the molecular chaperones heat shock protein (Hsp) 90alpha and beta as target genes of both pathways. Interestingly, in situ overexpression of both Hsp90 proteins was observed in the majority of MM, but not in MGUS or in normal plasma cells. SiRNA-mediated knockdown of Hsp90 or treatment with the novel Hsp90 inhibitor 17-DMAG attenuated the levels of phospho-STAT3 and phospho-ERK and decreased the viability of MM cells. Although knockdown of Hsp90beta unlike knockdown of Hsp90alpha was sufficient to induce apoptosis, this effect was strongly increased when both Hsp90s were targeted, indicating a cooperation of both. Given the importance of the bone marrow microenvironment for drug resistance and MM cell survival, apoptosis induced by Hsp90 inhibition was not mitigated in the presence of bone marrow stromal cells, osteoclasts or endothelial cells. These observations suggest, that a positive feedback loop consisting of Hsp90alpha/beta and major signaling pathways supports the survival of MM cells. Our results emphasize a role for Hsp90alpha and Hsp90beta in MM pathogenesis.