7-Dehydrocholesterol is an endogenous suppressor of ferroptosis.

Ferroptosis is a form of cell death that has received considerable attention not only as a means to eradicate defined tumour entities but also because it provides unforeseen insights into the metabolic adaptation that tumours exploit to counteract phospholipid oxidation1,2. Here, we identify proferroptotic activity of 7-dehydrocholesterol reductase (DHCR7) and an unexpected prosurvival function of its substrate, 7-dehydrocholesterol (7-DHC). Although previous studies suggested that high concentrations of 7-DHC are cytotoxic to developing neurons by favouring lipid peroxidation3, we now show that 7-DHC accumulation confers a robust prosurvival function in cancer cells. Because of its far superior reactivity towards peroxyl radicals, 7-DHC effectively shields (phospho)lipids from autoxidation and subsequent fragmentation. We provide validation in neuroblastoma and Burkitt's lymphoma xenografts where we demonstrate that the accumulation of 7-DHC is capable of inducing a shift towards a ferroptosis-resistant state in these tumours ultimately resulting in a more aggressive phenotype. Conclusively, our findings provide compelling evidence of a yet-unrecognized antiferroptotic activity of 7-DHC as a cell-intrinsic mechanism that could be exploited by cancer cells to escape ferroptosis.

Characterization and root cause analysis of immunogenicity to pasotuxizumab (AMG 212), a prostate-specific membrane antigen-targeting bispecific T-cell engager therapy.

Introduction: In oncology, anti-drug antibody (ADA) development that significantly curtails response durability has not historically risen to a level of concern. The relevance and attention ascribed to ADAs in oncology clinical studies have therefore been limited, and the extant literature on this subject scarce. In recent years, T cell engagers have gained preeminence within the prolific field of cancer immunotherapy. These drugs whose mode of action is expected to potently stimulate anti-tumor immunity, may potentially induce ADAs as an unintended corollary due to an overall augmentation of the immune response. ADA formation is therefore emerging as an important determinant in the successful clinical development of such biologics. Methods: Here we describe the immunogenicity and its impact observed to pasotuxizumab (AMG 212), a prostate-specific membrane antigen (PSMA)-targeting bispecific T cell engager (BiTE®) molecule in NCT01723475, a first-in-human (FIH), multicenter, dose-escalation study in patients with metastatic castration-resistant prostate cancer (mCRPC). To explain the disparity in ADA incidence observed between the SC and CIV arms of the study, we interrogated other patient and product-specific factors that may have explained the difference beyond the route of administration. Results: Treatment-emergent ADAs (TE-ADA) developed in all subjects treated with at least 1 cycle of AMG 212 in the subcutaneous (SC) arm. These ADAs were neutralizing and resulted in profound exposure loss that was associated with contemporaneous reversal of initial Prostate Surface Antigen (PSA) responses, curtailing durability of PSA response in patients. Pivoting from SC to a continuous intravenous (CIV) administration route remarkably yielded no subjects developing ADA to AMG 212. Through a series of stepwise functional assays, our investigation revealed that alongside a more historically immunogenic route of administration, non-tolerant T cell epitopes within the AMG 212 amino acid sequence were likely driving the high-titer, sustained ADA response observed in the SC arm. Discussion: These mechanistic insights into the AMG 212 ADA response underscore the importance of performing preclinical immunogenicity risk evaluation as well as advocate for continuous iteration to better our biologics.

Survival outcomes in patients with relapsed/refractory or MRD-positive B-cell acute lymphoblastic leukemia treated with blinatumomab.

Blinatumomab has demonstrated significant efficacy in adult and pediatric patients with relapsed/refractory B-cell acute lymphoblastic leukemia (R/R B-cell ALL) and patients with measurable residual disease (MRD). This review aimed to compare median relapse-free survival (RFS) and median overall survival (OS) in adult and pediatric patients with R/R or MRD-positive B-cell ALL from pivotal studies [MT-103-211 and TOWER for adults with Philadelphia chromosome (Ph)-negative R/R B-cell ALL, ALCANTARA for adults with Ph-positive R/R B-cell ALL, MT-103-203 for adults with MRD-positive B-cell ALL, and MT-103-205 for pediatric patients with R/R B-cell ALL], with the median RFS and OS from retrospective analyses, country or ethnicity-specific studies, and studies based on real-world evidence (RWE) identified from a literature search. Adults with Ph-negative R/R B-cell ALL who received blinatumomab as first salvage demonstrated a numerically longer median OS compared with that in patients from pivotal studies (MT-103-211 and TOWER) without additional safety concerns. In pediatric patients with R/R B-cell ALL treated with blinatumomab, the median RFS and OS from retrospective analyses and country/ethnicity-specific studies were comparable with the median RFS and OS from the pivotal study MT-103-205. The median RFS and OS from RWE studies in adults with R/R B-cell ALL were numerically longer than the median RFS and OS from pivotal studies (MT-103-211, TOWER, and ALCANTARA); however, this trend was not observed in pediatric patients with R/R B-cell ALL. In conclusion, this analysis identified first salvage adults with Ph-negative R/R B-cell ALL as particularly well-suited for treatment with blinatumomab since survival outcomes from retrospective analyses reported in this patient subgroup were numerically better compared with those from pivotal studies without additional safety signals.

Ancistrocladinium A Induces Apoptosis in Proteasome Inhibitor-Resistant Multiple Myeloma Cells: A Promising Therapeutic Agent Candidate.

The N,C-coupled naphthylisoquinoline alkaloid ancistrocladinium A belongs to a novel class of natural products with potent antiprotozoal activity. Its effects on tumor cells, however, have not yet been explored. We demonstrate the antitumor activity of ancistrocladinium A in multiple myeloma (MM), a yet incurable blood cancer that represents a model disease for adaptation to proteotoxic stress. Viability assays showed a potent apoptosis-inducing effect of ancistrocladinium A in MM cell lines, including those with proteasome inhibitor (PI) resistance, and in primary MM cells, but not in non-malignant blood cells. Concomitant treatment with the PI carfilzomib or the histone deacetylase inhibitor panobinostat strongly enhanced the ancistrocladinium A-induced apoptosis. Mass spectrometry with biotinylated ancistrocladinium A revealed significant enrichment of RNA-splicing-associated proteins. Affected RNA-splicing-associated pathways included genes involved in proteotoxic stress response, such as PSMB5-associated genes and the heat shock proteins HSP90 and HSP70. Furthermore, we found strong induction of ATF4 and the ATM/H2AX pathway, both of which are critically involved in the integrated cellular response following proteotoxic and oxidative stress. Taken together, our data indicate that ancistrocladinium A targets cellular stress regulation in MM and improves the therapeutic response to PIs or overcomes PI resistance, and thus may represent a promising potential therapeutic agent.

Pasotuxizumab, a BiTE® immune therapy for castration-resistant prostate cancer: Phase I, dose-escalation study findings.

Aim: We report results of a first-in-human study of pasotuxizumab, a PSMA bispecific T-cell engager (BiTE®) immune therapy mediating T-cell killing of tumor cells in patients with advanced castration-resistant prostate cancer. Patients & methods: We assessed once-daily subcutaneous (SC) pasotuxizumab. All SC patients developed antidrug antibodies; therefore, continuous intravenous (cIV) infusion was assessed. Results: A total of 47 patients received pasotuxizumab (SC: n = 31, 0.5-172 µg/d; cIV: n = 16, 5-80 µg/d). The SC maximum tolerated dose was 172.0 µg/d. A sponsor change stopped the cIV cohort early; maximum tolerated dose was not determined. PSA responders occurred (>50% PSA decline: SC, n = 9; cIV, n = 3), including two long-term responders. Conclusion: Data support pasotuxizumab safety in advanced castration-resistant prostate cancer and represent evidence of BiTE monotherapy efficacy in solid tumors. Clinical trial registration: NCT01723475 (ClinicalTrials.gov).

Long-term survival of patients with relapsed/refractory acute lymphoblastic leukemia treated with blinatumomab.

BACKGROUND: Blinatumomab is a CD19 BiTE (bispecific T-cell engager) immuno-oncology therapy that mediates the lysis of cells expressing CD19. METHODS: A pooled analysis of long-term follow-up data from 2 phase 2 studies that evaluated blinatumomab in heavily pretreated adults with Philadelphia chromosome-negative, relapsed/refractory B-cell precursor acute lymphoblastic leukemia was conducted. RESULTS: A total of 259 patients were included in the analysis. The median overall survival (OS) among all patients, regardless of response, was 7.5 months (95% confidence interval [CI], 5.5-8.5 months); the median follow-up time for OS was 36.0 months (range, 0.3-60.8 months). The median relapse-free survival (RFS) among patients who achieved a complete remission (CR) or complete remission with partial hematologic recovery (CRh) in the first 2 cycles (n = 123) was 7.7 months (95% CI, 6.2-10.0 months); the median follow-up time for RFS was 35.0 months (range, 9.5-59.5 months). OS and RFS plateaued with 3-year rates of 17.7% and 23.4%, respectively. The cumulative incidence function of the time to relapse, with death not due to relapse considered a competing risk, for patients who achieved a CR/CRh within 2 cycles of treatment also plateaued with a 3-year relapse rate of 59.3%. For patients who achieved a CR/CRh with blinatumomab followed by allogeneic hematopoietic stem cell transplantation while in continuous CR, the median OS was 18.1 months (95% CI, 10.3-30.0 months) with a 3-year survival rate of 37.2%. CONCLUSIONS: These data suggest that long-term survival is possible after blinatumomab therapy. LAY SUMMARY: Immuno-oncology therapies such as blinatumomab activate the patient's own immune system to kill cancer cells. This study combined follow-up data from 2 blinatumomab-related clinical trials to evaluate long-term survival in patients with relapsed and/or refractory B-cell precursor acute lymphoblastic leukemia at high risk for unfavorable outcomes. Among patients who achieved a deep response with blinatumomab, one-third lived 3 years or longer. These findings suggest that long-term survival is possible after treatment with blinatumomab.

RAL GTPases mediate multiple myeloma cell survival and are activated independently of oncogenic RAS.

Oncogenic RAS provides crucial survival signaling for up to half of multiple myeloma cases, but has so far remained a clinically undruggable target. RAL is a member of the RAS superfamily of small GTPases and is considered to be a potential mediator of oncogenic RAS signaling. In primary multiple myeloma, we found RAL to be overexpressed in the vast majority of samples when compared with pre-malignant monoclonal gammopathy of undetermined significance or normal plasma cells. We analyzed the functional effects of RAL abrogation in myeloma cell lines and found that RAL is a critical mediator of survival. RNAi-mediated knockdown of RAL resulted in rapid induction of tumor cell death, an effect which was independent from signaling via mitogen-activated protein kinase, but appears to be partially dependent on Akt activity. Notably, RAL activation was not correlated with the presence of activating RAS mutations and remained unaffected by knockdown of oncogenic RAS. Furthermore, transcriptome analysis yielded distinct RNA expression signatures after knockdown of either RAS or RAL. Combining RAL depletion with clinically relevant anti-myeloma agents led to enhanced rates of cell death. Our data demonstrate that RAL promotes multiple myeloma cell survival independently of oncogenic RAS and, thus, this pathway represents a potential therapeutic target in its own right.

Curative outcomes following blinatumomab in adults with minimal residual disease B-cell precursor acute lymphoblastic leukemia.

Minimal residual disease (MRD) is the strongest predictor of relapse in B-cell precursor acute lymphoblastic leukemia (BCP-ALL). In BLAST study (NCT01207388), adults with BCP-ALL in remission with MRD after chemotherapy received blinatumomab, a CD19 BiTE® immuno-oncotherapy, 15 µg/m2/day for up to four 6-week cycles (4 weeks continuous infusion, 2 weeks off). Survival was evaluated for 110 patients, including 74 who received HSCT in continuous complete remission. With a median follow-up of 59·8 months, median survival (months) was 36·5 (95% CI: 22.0-not reached [NR]). Median survival was NR (29.5-NR) for complete MRD responders (n = 84) and 14.4 (3.8-32.3) for MRD non-responders (n = 23; p = 0.002); after blinatumomab and HSCT, median survival was NR (25.7-NR) (n = 61) and 16.5 (1.1-NR) (n = 10; p = 0.065), respectively. This final analysis suggests complete MRD response during blinatumomab treatment is curative. Post-hoc analysis of study data suggests while post blinatumomab HSCT may be beneficial in appropriate patients, long-term survival without HSCT is also possible.

T cell-engaging therapies - BiTEs and beyond.

Immuno-oncology approaches have entered clinical practice, with tremendous progress particularly in the field of T cell-engaging therapies over the past decade. Herein, we provide an overview of the current status of bispecific T cell engager (BiTE) therapy, considering the unprecedented new indication for such therapy in combating minimal (or measurable) residual disease in patients with acute lymphoblastic leukaemia, and the development of novel approaches based on this concept. Key aspects that we discuss include the current clinical data, challenges relating to treatment administration and patient monitoring, toxicities and resistance to treatment, and novel strategies to overcome these hurdles as well as to broaden the indications for BiTE therapy, particularly to common solid cancers. Elucidation of mechanisms of resistance and immune escape and new technologies used in drug development pave the way for new and more-effective therapies and rational combinatorial approaches. In particular, we highlight novel therapeutic agents, such as bifunctional checkpoint-inhibitory T cell engagers (CiTEs), simultaneous multiple interaction T cell engagers (SMITEs), trispecific killer engagers (TriKEs) and BiTE-expressing chimeric antigen receptor (CAR) T cells (CART.BiTE cells), designed to integrate various immune functions into one molecule or a single cellular vector and thereby enhance efficacy without compromising safety. We also discuss the targeting of intracellular tumour-associated epitopes using bispecific constructs with T cell receptor (TCR)-derived, rather than an antibody-based, antigen-recognition domains, termed immune-mobilizing monoclonal TCRs against cancer (ImmTACs), which might broaden the armamentarium of T cell-engaging therapies.

The heat shock protein 70 inhibitor VER155008 suppresses the expression of HSP27, HOP and HSP90ß and the androgen receptor, induces apoptosis, and attenuates prostate cancer cell growth.

Heat shock proteins (HSPs) are molecular chaperones that play a pivotal role in correct folding, stabilization and intracellular transport of many client proteins including those involved in oncogenesis. HSP70, which is frequently overexpressed in prostate cancer (PCa), has been shown to critically contribute to tumor cell survival, and might therefore represent a potential therapeutic target. We treated both the androgen receptor (AR)-positive LNCaP and the AR-negative PC-3 cell lines with the pharmacologic HSP70 inhibitor VER155008. Although we observed antiproliferative effects and induction of apoptosis upon HSP70 inhibition, the apoptotic effect was more pronounced in AR-positive LNCaP cells. In addition, VER155008 treatment induced G1 cell cycle arrest in LNCaP cells and decreased AR expression. Further analysis of the HSP system by Western blot analysis revealed that expression of HSP27, HOP and HSP90ß was significantly inhibited by VER155008 treatment, whereas the HSP40, HSP60, and HSP90α expression remained unchanged. Taken together, VER155008 might serve as a novel therapeutic option in PCa patients independent of the AR expression status.

Adhesion of T Cells to Endothelial Cells Facilitates Blinatumomab-Associated Neurologic Adverse Events.

Blinatumomab, a CD19/CD3-bispecific T-cell engager (BiTE) immuno-oncology therapy for the treatment of B-cell malignancies, is associated with neurologic adverse events in a subgroup of patients. Here, we provide evidence for a two-step process for the development of neurologic adverse events in response to blinatumomab: (i) blinatumomab induced B-cell-independent redistribution of peripheral T cells, including T-cell adhesion to blood vessel endothelium, endothelial activation, and T-cell transmigration into the perivascular space, where (ii) blinatumomab induced B-cell-dependent T-cell activation and cytokine release to potentially trigger neurologic adverse events. Evidence for this process includes (i) the coincidence of T-cell redistribution and the early occurrence of most neurologic adverse events, (ii) T-cell transmigration through brain microvascular endothelium, (iii) detection of T cells, B cells, and blinatumomab in cerebrospinal fluid, (iv) blinatumomab-induced T-cell rolling and adhesion to vascular endothelial cells in vitro, and (v) the ability of antiadhesive agents to interfere with blinatumomab-induced interactions between T cells and vascular endothelial cells in vitro and in patients. On the basis of these observations, we propose a model that could be the basis of mitigation strategies for neurologic adverse events associated with blinatumomab treatment and other T-cell therapies. SIGNIFICANCE: This study proposes T-cell adhesion to endothelial cells as a necessary but insufficient first step for development of blinatumomab-associated neurologic adverse events and suggests interfering with adhesion as a mitigation approach.

Assessment of TP53 lesions for p53 system functionality and drug resistance in multiple myeloma using an isogenic cell line model.

Recent advances in molecular diagnostics have shown that lesions affecting both copies of the gene for tumor suppressor protein 53 (TP53) count among the most powerful predictors for high-risk disease in multiple myeloma (MM). However, the functional relevance and potential therapeutic implications of single hits to TP53 remain less well understood. Here, we have for the first time approximated the different constellations of mono- and bi-allelic TP53 lesions observed in MM patients within the frame of a single MM cell line model and assessed their potential to disrupt p53 system functionality and to impart drug resistance. Both types of common first hit: point mutation with expression of mutant p53 protein or complete loss of contribution from one of two wildtype alleles strongly impaired p53 system functionality and increased resistance to melphalan. Second hits abolished remaining p53 activity and increased resistance to genotoxic drugs even further. These results fit well with the clinical drive to TP53 single- and double-hit disease in MM patients, provide a rationale for the most commonly observed double-hit constellation (del17p+ TP53 point mutation), and underscore the potential increases in MM cell malignancy associated with any type of initial TP53 lesion.

On-target restoration of a split T cell-engaging antibody for precision immunotherapy.

T cell-engaging immunotherapies are changing the landscape of current cancer care. However, suitable target antigens are scarce, restricting these strategies to very few tumor types. Here, we report on a T cell-engaging antibody derivative that comes in two complementary halves and addresses antigen combinations instead of single molecules. Each half, now coined hemibody, contains an antigen-specific single-chain variable fragment (scFv) fused to either the variable light (VL) or variable heavy (VH) chain domain of an anti-CD3 antibody. When the two hemibodies simultaneously bind their respective antigens on a single cell, they align and reconstitute the original CD3-binding site to engage T cells. Employing preclinical models for aggressive leukemia and breast cancer, we show that by the combinatorial nature of this approach, T lymphocytes exclusively eliminate dual antigen-positive cells while sparing single positive bystanders. This allows for precision targeting of cancers not amenable to current immunotherapies.

Molecular response with blinatumomab in relapsed/refractory B-cell precursor acute lymphoblastic leukemia.

Minimal residual disease (MRD), where leukemic cell levels are lower than the morphologic detection threshold, is the most important prognostic factor for acute lymphoblastic leukemia (ALL) relapse during first-line chemotherapy treatment and is standard of care in treatment monitoring and decision making. Limited data are available on the prognostic value of MRD response after relapse. We evaluated the relationship between MRD response and outcomes in blinatumomab-treated adults with relapsed/refractory (R/R) B-cell precursor ALL. Of 90 patients with complete remission (CR) or CR with partial hematologic recovery (CRh), 64 (71.1%) achieved a complete MRD response (no detectable individual rearrangements of immunoglobulin/T-cell receptor genes by polymerase chain reaction [PCR] at a minimum sensitivity level of 10-4). Eleven patients had MRD <10-4. Therefore, overall, 75 (83.3%) experienced an MRD response (no detectable MRD or detectable MRD) measured by PCR within the first 2 treatment cycles. Overall survival (OS) and relapse-free survival (RFS) were significantly longer in patients who achieved CR/CRh and MRD response (median, 20.6 and 9.0 months, respectively) compared with CR/CRh patients without MRD response (median, 12.5 and 2.3 months, respectively). In conclusion, longer durations of OS and RFS associated with MRD response support the value of achieving MRD response and its use as a prognostic factor for blinatumomab treatment in R/R ALL. This trial was registered at www.clinicaltrials.gov as #NCT01466179.

Allogeneic transplantation in multiple myeloma: long-term follow-up and cytogenetic subgroup analysis.

This phase 3 trial compared tandem autologous stem cell transplantation (autoSCT) versus autoSCT followed by reduced-intensity conditioning allogeneic stem cell transplantation (auto/alloSCT) in patients with newly diagnosed multiple myeloma (MM) with deletion of (del) chromosome 13q (del13q). The availability/absence of a human leukocyte antigen-matched-related or matched-unrelated donor (MUD) determined the nature of the second SCT. The primary endpoint was progression-free survival (PFS) in the intention-to-treat population (n = 199). Auto/alloSCT was performed in 126 patients; 74 received MUD allografts. After 91 months median follow-up, median PFS with auto/allo versus tandem autoSCT was 34.5 versus 21.8 months (P = 0.003; adjusted hazard ratio 0.55, 95% confidence interval 0.36-0.84). Median overall survival (OS) was 70.2 versus 71.8 months (P = 0.856). Two-year non-relapse mortality with auto/allo versus tandem autoSCT was 14.3% versus 4.1% (P = 0.008). In patients harboring both del13q and del17p, median PFS and OS were 37.5 and 61.5 months with auto/allo (n = 19) versus 6.1 and 23.4 months with tandem autoSCT (n = 6) (P = 0.0002 and 0.032). Our findings suggest that auto/alloSCT significantly extends PFS versus tandem autoSCT in del13q MM, and indicate some survival benefit for first-line alloSCT in high-risk MM.

Long-term outcome of patients with relapsed/refractory B-cell non-Hodgkin lymphoma treated with blinatumomab.

Blinatumomab, the first-in-class CD3/CD19 bispecific T-cell engager antibody construct, has recently been approved for treating patients with relapsed or refractory (R/R) B-cell acute lymphoblastic leukemia. However, the clinical proof of concept of blinatumomab efficacy was initially demonstrated in patients with R/R B-cell non-Hodgkin lymphoma (B-NHL) in the MT103-104 phase 1 dose-escalation and expansion trial (NCT00274742), which defined 60 µg/m2 per day as the maximum tolerated dose (MTD). The clinically most relevant adverse effects were neurologic symptoms and cytokine release syndrome. Currently, there are no data on long-term outcomes and toxicity for B-NHL patients receiving blinatumomab treatment, so we performed a single-center, long-term follow-up analysis of 38 patients who participated in the MT103-104 phase 1 trial. We found no evidence for long-term toxicities, especially no blinatumomab-induced neurocognitive impairments. For the entire study population, the median overall survival (OS) was 4.6 years. Remarkably, patients who had received ≥60 µg/m2 per day and responded to blinatumomab achieved a median OS of 7.7 years. Of note, 6 of the surviving patients treated at the MTD have been treatment-free for more than 7 years. In contrast, patients who were treated at dose levels below the MTD had a median OS of only 1.1 years. These results indicate that 60 µg/m2 per day seems to represent the targeted dose level of blinatumomab required for durable remission in R/R B-NHL. Here, we provide the first clinical evidence that blinatumomab lacks long-term toxicity and has the potential to induce sustained remissions in patients with R/R B-NHL.