CALR-mutated patients with low allele burden represent a specific subtype of essential thrombocythemia: A study on behalf of FIM and GBMHM

A low allele burden (i.e., <20%) of the CALR driver mutation is found in 10.8% of CALR-mutated MPNs, mostly in essential thrombocythemia, and correlates with a milder phenotype and a more indolent evolution compared to patients with an allele burden ≥20%.

INA03, a potent transferrin-competitive antibody-drug conjugate against CD71, for a safer acute leukemia treatment

Innovative strategies to enhance efficacy and overcome drug resistance in hematologic cancers such as antibody-drug conjugates (ADCs) have shifted the paradigm of conventional care by delivering promising outcomes in cancer therapies with a significant reduction in the risk of relapse. The transferrin receptor 1, CD71, known to be overexpressed in malignant cells, is considered a potent anti-tumoral target. Therefore, we have developed an anti-CD71 ADC, INA03, a humanized antibody conjugated to the monomethyl auristatin E (MMAE) through a 3-arylpropiolonitrile-valine-citruline linker. In this study, we investigated both potency and safety of INA03, in competition with transferrin (Tf), the CD71's natural ligand, as a novel strategy to specifically target highly proliferative cells. The high expression of CD71 was confirmed on different leukemic cell lines, allowing INA03 to bind efficiently. Subsequently, INA03 rapidly internalizes into lysosomal compartments, where its cytotoxic drug is released following cathepsin-B cleavage. Downregulating CD71 expression using shRNA highlighted that INA03-induced cell death was dependent on CD71 density at the cell surface. INA03 intravenous treatment in acute leukemia mouse models significantly reduced tumor burden, increased mice survival and showed no residual disease compared to conventional chemotherapies. Since INA03 competes with the human Tf, a double knock-in (hCD71/hTf) competent mouse model was generated to mimic human pharmacokinetics and pharmacodynamics. INA03 administration in hCD71/hTf mice did not reveal, even at high doses, any improper toxicities. Hence, these data demonstrate promising pre-clinical efficacy and safety of INA03 and support its development as a novel acute leukemia treatment.

Comparative clinical and molecular landscape of primary and secondary myelofibrosis: Superior performance of MIPSS70+ v2.0 over MYSEC-PM

Comparative clinical characteristics, molecular landscape and prognosis scoring for primary (PMF) and secondary myelofibrosis (SMF).

Distinct clinico-molecular arterial and venous thrombosis scores for myeloproliferative neoplasms risk stratification

Current recommended risk scores to predict thrombotic events associated with myeloproliferative neoplasms (MPN) do not discriminate between arterial and venous thrombosis despite their different physiopathology. To define novel stratification systems, we delineated a comprehensive landscape of MPN associated thrombosis across a large long-term follow-up MPN cohort. Prior arterial thrombosis, age >60 years, cardiovascular risk factors and presence of TET2 or DNMT3A mutations were independently associated with arterial thrombosis in multivariable analysis. ARTS, an ARterial Thrombosis Score, based on these four factors, defined low- (0.37% patients-year) and high-risk (1.19% patients-year) patients. ARTS performance was superior to the two-tiered conventional risk stratification in our training cohort, across all MPN subtypes, as well as in two external validation cohorts. Prior venous thrombosis and presence of a JAK2V617F mutation with a variant allelic frequency ≥50% were independently associated with venous thrombosis. The discrimination potential of VETS, a VEnous Thrombosis Score based on these two factors, was poor, similar to the two-tiered conventional risk stratification. Our study pinpoints arterial and venous thrombosis clinico-molecular differences and proposes an arterial risk score for more accurate patients' stratification. Further improvement of venous risk scores, accounting for additional factors and considering venous thrombosis as a heterogeneous entity is warranted.

Clonal architecture evolution in Myeloproliferative Neoplasms: from a driver mutation to a complex heterogeneous mutational and phenotypic landscape

Myeloproliferative neoplasms are characterized by the acquisition at the hematopoietic stem cell level of driver mutations targeting the JAK/STAT pathway. In addition, they also often exhibit additional mutations targeting various pathways such as intracellular signalling, epigenetics, mRNA splicing or transcription. The natural history of myeloproliferative neoplasms is usually marked by a chronic phase of variable duration depending on the disease subtype, which can be followed by an accelerated phase or transformation towards more aggressive diseases such as myelofibrosis or acute leukemia. Besides, recent studies revealed important new information about the rates and mechanisms of sequential acquisition and selection of mutations in hematopoietic cells of myeloproliferative neoplasms. Better understanding of these events has been made possible in large part with the help of novel techniques that are now available to precisely decipher at the single cell level both the clonal architecture and the mutation-induced cell modifications. In this review, we will summarize the most recent knowledge about the mechanisms leading to clonal selection, how clonal architecture complexity can explain disease heterogeneity, and the impact of clonal evolution on clinical evolution.

Impact of the COVID-19 pandemic on antiviral drug development for other community-acquired respiratory viruses’ infections

The coronavirus disease 2019 (COVID-19) pandemic indirectly resulted in missed therapeutic opportunities for many diseases. Here we focus on community-acquired respiratory viruses other than severe acute respiratory syndrome coronavirus 2 (SARS-CoV2) [respiratory syncytial virus, parainfluenza and influenza A], and highlight the pandemics impact on clinical trials to develop novel therapies for other severe respiratory viral infections. We retrospectively reviewed inclusion rates within respiratory antiviral clinical trials in comparison with all other clinical trials in our clinical investigations center, before and during the COVID-19 pandemic. As opposed to the remaining clinical trials developed within our unit, respiratory antiviral trials inclusion rates did not recover after the initial recruitment decrease observed across all trials during the first pandemic wave. These results were discussed in the context of non-COVID-19 respiratory viral infection rates within our center, showing a general decline in seasonal respiratory viruses spread since the COVID-19 pandemic onset. Virus epidemiology changes upon the wide SARS-CoV-2 expansion as well as the lifestyle changes globally adopted to prevent SARS-CoV-2 transmission could have therefore contributed to the negative impact of the COVID-19 pandemic on antiviral drug development. Our study highlights the peculiarity of respiratory antiviral drug development during the COVID-19 pandemic era and describes potential explanations for such drug development halting.

Unleashing Cell-Intrinsic Inflammation as a Strategy to Kill AML Blasts

Leukemic blasts are immune cells gone awry. We hypothesized that dysregulation of inflammatory pathways contributes to the maintenance of their leukemic state and can be exploited as cell-intrinsic, self-directed immunotherapy. To this end, we applied genome-wide screens to discover genetic vulnerabilities in acute myeloid leukemia (AML) cells implicated in inflammatory pathways. We identified the immune modulator IRF2BP2 as a selective AML dependency. We validated AML cell dependency on IRF2BP2 with genetic and protein degradation approaches in vitro and genetically in vivo. Chromatin and global gene-expression studies demonstrated that IRF2BP2 represses IL1β/TNFα signaling via NFκB, and IRF2BP2 perturbation results in an acute inflammatory state leading to AML cell death. These findings elucidate a hitherto unexplored AML dependency, reveal cell-intrinsic inflammatory signaling as a mechanism priming leukemic blasts for regulated cell death, and establish IRF2BP2-mediated transcriptional repression as a mechanism for blast survival.

SIGNIFICANCE

This study exploits inflammatory programs inherent to AML blasts to identify genetic vulnerabilities in this disease. In doing so, we determined that AML cells are dependent on the transcriptional repressive activity of IRF2BP2 for their survival, revealing cell-intrinsic inflammation as a mechanism priming leukemic blasts for regulated cell death. See related commentary by Puissant and Medyouf, p. 1617. This article is highlighted in the In This Issue feature, p. 1599.

P2RY2-AKT activation is a therapeutically actionable consequence of XPO1 inhibition in acute myeloid leukemia

Selinexor is a first-in-class inhibitor of the nuclear exportin XPO1 that was recently approved by the US Food and Drug Administration for the treatment of multiple myeloma and diffuse large B-cell lymphoma. In relapsed/refractory acute myeloid leukemia (AML), selinexor has shown promising activity, suggesting that selinexor-based combination therapies may have clinical potential. Here, motivated by the hypothesis that selinexor's nuclear sequestration of diverse substrates imposes pleiotropic fitness effects on AML cells, we systematically catalog the pro- and anti-fitness consequences of selinexor treatment. We discover that selinexor activates PI3Kγ-dependent AKT signaling in AML by upregulating the purinergic receptor P2RY2. Inhibiting this axis potentiates the anti-leukemic effects of selinexor in AML cell lines, patient-derived primary cultures and multiple mouse models of AML. In a syngeneic, MLL-AF9-driven mouse model of AML, treatment with selinexor and ipatasertib outperforms both standard-of-care chemotherapy and chemotherapy with selinexor. Together, these findings establish drug-induced P2RY2-AKT signaling as an actionable consequence of XPO1 inhibition in AML.

The challenge of targets and drug discovery using large-scale screening approaches in onco-hematology

Target identification and drug discovery roads have been widely improved over the past decades in onco-hematology. In this review, we summarize recent improvements in the use of physio-pathologically relevant models and innovative screening approaches to accelerate efficient drug development. Using acute myeloid leukemia as an example, we also discuss the main encountered pitfalls and propose alternative roads to improve the drug discovery journey in onco-hematology.

Targeting acute myeloid leukemia dependency on VCP-mediated DNA repair through a selective second-generation small-molecule inhibitor

The development and survival of cancer cells require adaptive mechanisms to stress. Such adaptations can confer intrinsic vulnerabilities, enabling the selective targeting of cancer cells. Through a pooled in vivo short hairpin RNA (shRNA) screen, we identified the adenosine triphosphatase associated with diverse cellular activities (AAA-ATPase) valosin-containing protein (VCP) as a top stress-related vulnerability in acute myeloid leukemia (AML). We established that AML was the most responsive disease to chemical inhibition of VCP across a panel of 16 cancer types. The sensitivity to VCP inhibition of human AML cell lines, primary patient samples, and syngeneic and xenograft mouse models of AML was validated using VCP-directed shRNAs, overexpression of a dominant-negative VCP mutant, and chemical inhibition. By combining mass spectrometry-based analysis of the VCP interactome and phospho-signaling studies, we determined that VCP is important for ataxia telangiectasia mutated (ATM) kinase activation and subsequent DNA repair through homologous recombination in AML. A second-generation VCP inhibitor, CB-5339, was then developed and characterized. Efficacy and safety of CB-5339 were validated in multiple AML models, including syngeneic and patient-derived xenograft murine models. We further demonstrated that combining DNA-damaging agents, such as anthracyclines, with CB-5339 treatment synergizes to impair leukemic growth in an MLL-AF9-driven AML murine model. These studies support the clinical testing of CB-5339 as a single agent or in combination with standard-of-care DNA-damaging chemotherapy for the treatment of AML.

[An example of Clinical Investigations Center reorganization during the COVID-19 pandemic French national lockdown]

Contexte

Le Centre d’investigations cliniques de l’Hôpital Saint-Louis (CIC-1427) est une structure dédiée qui accueille des patients inclus dans des essais cliniques essentiellement de phases précoces (première administration chez l’homme, phases I et II). Ces patients sont accueillis dans des locaux autorisés et validés par l’Agence régionale de santé (ARS). En mars 2020, face à la pandémie de la COVID-19 et aux mesures de confinement national de la population décidées, par le gouvernement français, le CIC-1427 a dû adapter rapidement ses procédures de fonctionnement pour assurer la sécurité des patients et de son personnel.

Objectif

Assurer une prise en charge optimale des patients inclus dans les essais cliniques de phases précoces, tout en respectant les bonnes pratiques cliniques (BPC) et les bonnes pratiques professionnelles des CIC (BPP des CIC), les exigences des promoteurs de chaque protocole, la sécurité des patients et du personnel multidisciplinaire (infirmiers, aide-soignants [AS], assistants de recherche clinique [ARC], coordonnateur d’études cliniques [CEC]), chefs de projets, cadre de santé et médecins investigateurs), dans le contexte de la crise sanitaire liée à la COVID-19.

Méthodes et résultats

De par son activité, nécessitant des tâches en présentiel, chaque personnel de l’équipe spécialisée en recherche clinique du CIC-1427 a dû adapter son activité quotidienne aux contraintes de la crise sanitaire. De nouvelles procédures spécifiques ont été rapidement élaborées, pour faire face à la pandémie. La plupart des visites médicales sur site ont été remplacées par des téléconsultations avec bilans biologiques dans les laboratoires de proximité, les « remote monitoring » ont remplacé les visites de monitoring sur site, les traitements ont été envoyés au domicile de chaque patient via des coursiers après accord des CPP (Comité de protection des personnes) de chaque protocole. Les visites indispensables ont pu être maintenues sur site grâce à l’implication sans faille de notre équipe soignante et sous condition de mise en place d’un protocole sanitaire adapté.

Conclusion

Grâce à l’implication de l’ensemble de notre équipe de recherche multidisciplinaire, et malgré les difficultés rencontrées, chaque patient a pu bénéficier d’un suivi personnalisé et poursuivre son traitement protocolaire. Les procédures mises en place ont également permis la collecte d’un maximum de données de sécurité et d’efficacité pour les promoteurs des essais cliniques et le respect des bonnes pratiques réglementaires. L’ensemble de ces mesures prises dans le contexte de l’urgence sanitaire, lors de la première vague épidémique, ont permis d’aborder plus sereinement la suite de l’épidémie.

Among classic myeloproliferative neoplasms, essential thrombocythemia is associated with the greatest risk of venous thromboembolism during COVID-19

In a multicenter European retrospective study including 162 patients with COVID-19 occurring in essential thrombocythemia (ET, n = 48), polycythemia vera (PV, n = 42), myelofibrosis (MF, n = 56), and prefibrotic myelofibrosis (pre-PMF, n = 16), 15 major thromboses (3 arterial and 12 venous) were registered in 14 patients, of whom all, but one, were receiving LMW-heparin prophylaxis. After adjustment for the competing risk of death, the cumulative incidence of arterial and venous thromboembolic events (VTE) reached 8.5% after 60 days follow-up. Of note, 8 of 12 VTE were seen in ET. Interestingly, at COVID-19 diagnosis, MPN patients had significantly lower platelet count (p < 0.0001) than in the pre-COVID last follow-up.This decline was remarkably higher in ET (-23.3%, p < 0.0001) than in PV (-16.4%, p = 0.1730) and was associated with higher mortality rate (p = 0.0010) for pneumonia. The effects of possible predictors of thrombosis, selected from those clinically relevant and statistically significant in univariate analysis, were examined in a multivariate model. Independent risk factors were transfer to ICU (SHR = 3.73, p = 0.029), neutrophil/lymphocyte ratio (SHR = 1.1, p = 0.001) and ET phenotype (SHR = 4.37, p = 0.006). The enhanced susceptibility to ET-associated VTE and the associated higher mortality for pneumonia may recognize a common biological plausibility and deserve to be delved to tailor new antithrombotic regimens including antiplatelet drugs.

High mortality rate in COVID-19 patients with myeloproliferative neoplasms after abrupt withdrawal of ruxolitinib

We report the clinical presentation and risk factors for survival in 175 patients with myeloproliferative neoplasms (MPN) and COVID-19, diagnosed between February and June 2020. After a median follow-up of 50 days, mortality was higher than in the general population and reached 48% in myelofibrosis (MF). Univariate analysis, showed a significant relationship between death and age, male gender, decreased lymphocyte counts, need for respiratory support, comorbidities and diagnosis of MF, while no association with essential thrombocythemia (ET), polycythemia vera (PV), and prefibrotic-PMF (pre-PMF) was found. Regarding MPN-directed therapy ongoing at the time of COVID-19 diagnosis, Ruxolitinib (Ruxo) was significantly more frequent in patients who died in comparison with survivors (p = 0.006). Conversely, multivariable analysis found no effect of Ruxo alone on mortality, but highlighted an increased risk of death in the 11 out of 45 patients who discontinued treatment. These findings were also confirmed in a propensity score matching analysis. In conclusion, we found a high risk of mortality during COVID-19 infection among MPN patients, especially in MF patients and/or discontinuing Ruxo at COVID-19 diagnosis. These findings call for deeper investigation on the role of Ruxo treatment and its interruption, in affecting mortality in MPN patients with COVID-19.

The Folate Cycle Enzyme MTHFR Is a Critical Regulator of Cell Response to MYC-Targeting Therapies

Deciphering the impact of metabolic intervention on response to anticancer therapy may elucidate a path toward improved clinical responses. Here, we identify amino acid-related pathways connected to the folate cycle whose activation predicts sensitivity to MYC-targeting therapies in acute myeloid leukemia (AML). We establish that folate restriction and deficiency of the rate-limiting folate cycle enzyme MTHFR, which exhibits reduced-function polymorphisms in about 10% of Caucasians, induce resistance to MYC targeting by BET and CDK7 inhibitors in cell lines, primary patient samples, and syngeneic mouse models of AML. Furthermore, this effect is abrogated by supplementation with the MTHFR enzymatic product CH₃-THF. Mechanistically, folate cycle disturbance reduces H3K27/K9 histone methylation and activates a SPI1 transcriptional program counteracting the effect of BET inhibition. Our data provide a rationale for screening MTHFR polymorphisms and folate cycle status to nominate patients most likely to benefit from MYC-targeting therapies. SIGNIFICANCE: Although MYC-targeting therapies represent a promising strategy for cancer treatment, evidence of predictors of sensitivity to these agents is limited. We pinpoint that folate cycle disturbance and frequent polymorphisms associated with reduced MTHFR activity promote resistance to BET inhibitors. CH₃-THF supplementation thus represents a low-risk intervention to enhance their effects.See related commentary by Marando and Huntly, p. 1791.This article is highlighted in the In This Issue feature, p. 1775.

Exploiting an Asp-Glu "switch" in glycogen synthase kinase 3 to design paralog-selective inhibitors for use in acute myeloid leukemia

Glycogen synthase kinase 3 (GSK3), a key regulatory kinase in the wingless-type MMTV integration site family (WNT) pathway, is a therapeutic target of interest in many diseases. Although dual GSK3α/β inhibitors have entered clinical trials, none has successfully translated to clinical application. Mechanism-based toxicities, driven in part by the inhibition of both GSK3 paralogs and subsequent β-catenin stabilization, are a concern in the translation of this target class because mutations and overexpression of β-catenin are associated with many cancers. Knockdown of GSK3α or GSK3β individually does not increase β-catenin and offers a conceptual resolution to targeting GSK3: paralog-selective inhibition. However, inadequate chemical tools exist. The design of selective adenosine triphosphate (ATP)-competitive inhibitors poses a drug discovery challenge due to the high homology (95% identity and 100% similarity) in this binding domain. Taking advantage of an Asp¹³³→Glu¹⁹⁶ "switch" in their kinase hinge, we present a rational design strategy toward the discovery of paralog-selective GSK3 inhibitors. These GSK3α- and GSK3β-selective inhibitors provide insights into GSK3 targeting in acute myeloid leukemia (AML), where GSK3α was identified as a therapeutic target using genetic approaches. The GSK3α-selective compound BRD0705 inhibits kinase function and does not stabilize β-catenin, mitigating potential neoplastic concerns. BRD0705 induces myeloid differentiation and impairs colony formation in AML cells, with no apparent effect on normal hematopoietic cells. Moreover, BRD0705 impairs leukemia initiation and prolongs survival in AML mouse models. These studies demonstrate feasibility of paralog-selective GSK3α inhibition, offering a promising therapeutic approach in AML.

Prognostic factors and outcome of patients with hematological malignancies in phase I trials: the Gustave Roussy scoring system

Despite considerable progress in hematological malignancies (HM) biology during the last decades, translation into clinical benefit remains a major challenge. To improve patient selection and identify patients most likely to benefit from phase I trials, we designed and validated, in an independent cohort, a simple prognostic score. Treatment outcome, toxicity, and survival data from 82 consecutive patients enrolled in 14 phase I trials were reviewed (January 2008-February 2012). We validated these results on a prospectively collected cohort (17 phase I trials, February 2012-May 2014, 88 patients). Within a median follow-up of 19.1 months (range: 2.1-43.8 months), the median progression-free and overall survival (OS) were, respectively, 4.1 months [95% confidence interval (CI): 3.0-5.3] and 19.8 months (95% CI: 16.1-36.8). Best overall response and disease control rates were similar to HM salvage regimens (28 and 64%, respectively). Through multivariate analysis of independent prognostic factors, we designed and prospectively validated a simple prognostic score based on histological subtype, performance status, and albumin. Patients with a low-risk score experienced significantly better OS compared with patients with an intermediate or a high score (median OS: 37 vs. 17 vs. 5 months; hazard ratio=11.68, 95% CI: 4.09-33.3). Our data indicate the safety and efficacy of phase I trials in a significant number of relapsed/refractory HM patients, with clinical benefit achieved in more than half of patients. Our simple scoring system offers a valuable selection tool encouraging HM patient inclusions in phase I trials.

Evaluation of Improved Glycogen Synthase Kinase-3α Inhibitors in Models of Acute Myeloid Leukemia

The challenge for glycogen synthase kinase-3 (GSK-3) inhibitor design lies in achieving high selectivity for one isoform over the other. The therapy of certain diseases, such as acute myeloid leukemia (AML), may require α-isoform specific targeting. The scorpion shaped GSK-3 inhibitors developed by our group achieved the highest GSK-3α selectivity reported so far but suffered from insufficient aqueous solubility. This work presents the solubility-driven optimization of our isoform-selective inhibitors using a scorpion shaped lead. Among 15 novel compounds, compound 27 showed high activity against GSK-3α/β with the highest GSK-3α selectivity reported to date. Compound 27 was profiled for bioavailability and toxicity in a zebrafish embryo phenotype assay. Selective GSK-3α targeting in AML cell lines was achieved with compound 27, resulting in a strong differentiation phenotype and colony formation impairment, confirming the potential of GSK-3α inhibition in AML therapy.

Partial Response at Completion of Bortezomib-Thalidomide-Dexamethasone (VTd) Induction Regimen Upfront in Multiple Myeloma Does Not Preclude Response to VTd in Consolidation

The impact of consolidation on response rates and PFS has recently been demonstrated after induction and autotransplantation upfront in Multiple Myeloma (MM). We further showed that patients in ≥VGPR following the intensification procedure benefited most from consolidation. Question remains as to the benefit of consolidation for patients in PR at completion of induction - feature of partial resistance to the induction regimen.

We collected data from 54 newly diagnosed MM treated with VTd-auto-VTd regimen that reached only PR at completion of the induction procedure.

Overall, 37 patients (68%) improved depth of response (≥VGPR) at completion of consolidation, including 35% that reached CR and 38% solely related to consolidation. Of patients that remained on PR or improved depth of response after ASCT, 26% and 38% further responded to consolidation, respectively. With a median follow-up of 36 months, improved depth of response translated into lower relapse rate compared with patients remaining in PR, 19% vs. 36%. This difference was more striking in patients that reached CR vs. others, 8% and 38%, respectively (p=0.039). The median TTP was prolonged in patients that improved depth of response after consolidation (p=0.012), with a 3-year TTP of 87% vs. 18% otherwise. In multivariate analysis, lack of improved depth of response to consolidation independently predicted shorten median TTP [OR=4.4, 95%CI=1-21; p=0.039], with elevated LDH and beta2m, and adverse FISH.

This study shows that VTd consolidation should be recommended to patients solely on PR at completion of induction with VTd, feature of lower sensitivity to VTd.

Rare melanocortin-3 receptor mutations with in vitro functional consequences are associated with human obesity

In contrast to the melanocortin 4 receptor, the possible role of the melanocortin 3 receptor (MC3R) in regulating body weight is still debated. We have previously reported three mutations in the MC3R gene showing association with human obesity, but these results were not confirmed in a study of severe obese North American adults. In this study, we evaluated the entire coding region of MC3R in 839 severely obese subjects and 967 lean controls of Italian and French origin. In vitro functional analysis of the mutations detected was also performed. The total prevalence of rare MC3R variants was not significantly different in obese subjects when compared with controls (P= 0.18). However, the prevalence of mutations with functional alterations was significantly higher in the obese group (P= 0.022). In conclusions, the results of this large study demonstrate that in the populations studied functionally significant MC3R variants are associated with obesity supporting the current hypothesis that rare variants might have a stronger impact on the individual susceptibility to gain weight. They also underline the importance of detailed in vitro functional studies in order to prove the pathogenic effect of such variants. Further investigations in larger cohorts will be needed in order to define the specific phenotypic characteristics potentially correlated with reduced MC3R signalling.