Tag Archives: JAK inhibitor

JAK Inhibitor–Based Combinations Could Represent the Next Frontier in Myelofibrosis

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Ryan Scott

In an interview with OncLive® following the Vanderbilt Stem Cell Transplant and Cellular Therapy Symposium, Ashwin Kishtagari, MD, discussed advancements in the treatment of patients with intermediate-risk to high-risk myelofibrosis and highlighted recent data from the 2023 ASH Annual Meeting for combination therapies using JAK inhibitors.

Studies presented at the meeting included the phase 3 TRANSFORM-1 clinical trial (NCT04472598)evaluating navitoclax plus ruxolitinib (Jakafi), as well as the phase 3 MANIFEST-2 trial (NCT04603495) investigating pelabresib (CPI-0610) in combination with ruxolitinib.1,2

Kishtagari, who serves as an assistant professor of medicine in the Department of Hematology and Oncology at Vanderbilt University Medical Center, as well as a clinical research fellow in Bick Lab at Vanderbilt University School of Medicine in Nashville, Tennessee, provided further updates on JAK inhibitors for the treatment of patients with myelofibrosis in another interview with OncLive.

OncLive: How do you see the treatment paradigm for myelofibrosis evolving in the future?

Kishtagari: We have 4 JAK inhibitors which are FDA approved for the treatment of [patients with] myelofibrosis, with the first being ruxolitinib. Fedratinib [Inrebic] was the second agent approved in 2019. Pacritinib [Vonjo] was approved by the FDA in 2022, and momelotinib [Ojjaara]was approved in 2023.

We are moving toward combination therapies because our goal is to have a more significant improvement in splenomegaly response and symptom improvement. The whole field of myelofibrosis is moving toward combination therapy, especially for patients with higher- or intermediate-risk myelofibrosis.

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Momelotinib Improves Anemia in JAK Inhibitor-Naive Myelofibrosis

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Sabrina Serani

Treatment with momelotinib (Ojjaara) delivered benefits to anemia among patients with myelofibrosis who were naive to JAK inhibitors, regardless of their baseline hemoglobin level. Further, momelotinib provided significant anemia benefits compared with ruxoltinib (Jakafi), according to an analysis from the phase 3 SIMPLIFY-1 study (NCT01969838).

SIMPLIFY-3 randomized 432 patients with myelofibrosis who had not received JAK inhibitors toreceive momelotinib or ruxolitinib.In patients who were anemic and received momelotinib, mean hemoglobin levels increased by weeks 2 to 4 of treatment, and hemoglobin levels remained stable among patients who were not anemic.

Comparatively, patients who were anemic and nonanemictreated with ruxolitinib experienced an initial decrease in mean hemoglobin. This decrease stabilized after weeks 4 to 6 as patients received red blood cell transfusions. Patients receiving ruxolitinib were permitted to cross over to the momelotinib group, and mean hemoglobin levels increased after this change.

The study also evaluated patients at different levels of anemia. Among patient who were mildly anemic, with ahemoglobin levelbetween 10 and 12 g/dL, 90.4% of patients were transfusion-free at baseline, 93.9% of these patients remained transfusion-free while receiving momelotinib. Four patients who were not transfusion-free at baseline became transfusion-free while on treatment. In contrast, patients who were mildly anemic in the ruxolitinib arm became more dependent on transfusion; 50% of patients who were transfusion-free at baseline required a transfusion while on ruxolitinib.

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A new mouse model highlights the need for better JAK inhibitors in myeloproliferative neoplasms

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Charles E. de Bock

The discovery that the gain of function JAK2 V617F mutation is present in myeloproliferative neoplasms (MPNs) has led to numerous clinical trials assessing the efficacy of JAK inhibitors. Most notably, ruxolitinib, a combined JAK1/2 selective inhibitor, has gained approval in patients with myeolofibrosis (MF), and additional JAK2 inhibitors including fedratinib, pacritinib, and momelotinib also under evaluation for patients with MF. However, while these inhibitors demonstrate some clinical benefit, they do not adequately reduce the mutant clone fraction. 1 , 2 Consequently, a critical question for the field has been whether the lack of a durable response is attributed to either (i) the inability of current JAK inhibitors to completely block the pathway or (ii) the possibility that mutant clones are not entirely dependent on this activated pathway.

To address these two possibilities, a new study from the laboratory of Ross Levine, published in Cancer Discovery,developed an innovative mouse model of Jak2 V617F alone or in combination with Tet2 loss. The novel aspect of this mouse model lies in the ability to control the expression and genetic deletion of Jak2 V617F allele from mutant clones upon development of MPN. To do so, it utilizes two orthogonal site‐specific recombinases which exert precise control over the temporal expression and deletion of the Jak2 V617F allele.

The mouse model uses the well‐established Cre recombinase that recognises short nucleotide target sequences called Lox sites, in conjunction with the relatively new Dre recombinase which recognizes short nucleotide sequences called Rox sites. Importantly, the strategic arrangement and orientation of these sequences can lead to either flipping or deletion of the intervening DNA sequence. In this context, Dre recombinase is employed to initiate the expression of the Jak2 V617F allele. Subsequently, a modified CreER recombinase, translocated to the nucleus upon tamoxifen treatment, can delete the Jak2 V617F allele (Figure 1A). This intricate mouse model provided a powerful tool for comparing the durability of response between JAK inhibitors and the genetic loss of Jak2 V617F in the context of MPNs.

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Next-Generation JAK Inhibitors Signal the Future of Myelofibrosis Treatment Advances

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Ashling Wahner

Newer-generation JAK inhibitors are increasingly adept at controlling symptoms in patients with myelofibrosis and may recapture treatment response in patients who have progressed on prior ruxolitinib (Jakafi), according to Joseph G. Jurcic, MD.

“Using drugs that target all these particular abnormalities can result in symptom and spleen improvement, and in some, a reduction in cytokines and allelic burden,” Jurcic said in an interview with OncLive®.

In the interview, Jurcic discussed the benefits and limitations of several JAK inhibitors for patients with myelofibrosis, highlighting the treatment advances that have been made since the introduction of ruxolitinib to the treatment paradigm, considerations for the use of fedratinib (Inrebic), and the potential advantages of pacritinib (Vonjo) for patients with anemia.

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Molecular Genetic Profile of Myelofibrosis: Implications in the Diagnosis, Prognosis, and Treatment Advancements

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by Tanvi Verma 1, Nikolaos Papadantonakis2, Deniz Peker Barclift1 and Linsheng Zhang

Simple Summary

Myelofibrosis refers to fibrosis in the bone marrow associated with certain bone marrow cancers. It is a characteristic of primary myelofibrosis and may develop later in other bone marrow cancers with overproduction of blood cells, such as polycythemia vera and essential thrombocythemia. It has been confirmed that mutations in three key genes, Janus kinase 2 (JAK2), calreticulin (CALR), and myeloproliferative leukemia oncogene (MPL), can increase the activity of blood-producing cells, make them grow more actively, and are associated with the development of myelofibrosis. Approximately 80% of myelofibrosis cases carry additional mutations that often involve proteins that control how genes are turned on and off. The presence of mutations provides evidence of a cancerous process. The order in which these mutations occur can influence how the disease manifests. Studies have shown that fibrosis is secondary to the cancerous process and is closely linked to abnormal cell growth driven by mutations. Sophisticated scoring systems have been developed to guide treatment decisions. Specific mutations and genetic changes significantly affect the scores and survival of individual patients. Currently, common treatment involves JAK inhibitors, which can help improve clinical symptoms; however, only a small number of patients show significant alleviation in the biology of the malignant process. New treatments being explored in clinical trials include drugs that target the regulation of genes and substances that modulate the immune system or inflammatory processes. Combining these with JAK inhibitors shows promising results, especially in patients with complex genetic profiles. In the future, by studying more genes, it is expected that researchers will uncover the reasons behind cases where mutations are not found in the three key genes and understand how genetic changes are connected to variable disease presentations, ultimately guiding personalized treatment plans for better outcomes with a chance for cures.

Abstract

Myelofibrosis (MF) is an essential element of primary myelofibrosis, whereas secondary MF may develop in the advanced stages of other myeloid neoplasms, especially polycythemia vera and essential thrombocythemia. Over the last two decades, advances in molecular diagnostic techniques, particularly the integration of next-generation sequencing in clinical laboratories, have revolutionized the diagnosis, classification, and clinical decision making of myelofibrosis. Driver mutations involving JAK2, CALR, and MPL induce hyperactivity in the JAK-STAT signaling pathway, which plays a central role in cell survival and proliferation. Approximately 80% of myelofibrosis cases harbor additional mutations, frequently in the genes responsible for epigenetic regulation and RNA splicing. Detecting these mutations is crucial for diagnosing myeloproliferative neoplasms (MPNs), especially in cases where no mutations are present in the three driver genes (triple-negative MPNs). While fibrosis in the bone marrow results from the disturbance of inflammatory cytokines, it is fundamentally associated with mutation-driven hematopoiesis. The mutation profile and order of acquiring diverse mutations influence the MPN phenotype. Mutation profiling reveals clonal diversity in MF, offering insights into the clonal evolution of neoplastic progression. Prognostic prediction plays a pivotal role in guiding the treatment of myelofibrosis. Mutation profiles and cytogenetic abnormalities have been integrated into advanced prognostic scoring systems and personalized risk stratification for MF. Presently, JAK inhibitors are part of the standard of care for MF, with newer generations developed for enhanced efficacy and reduced adverse effects. However, only a minority of patients have achieved a significant molecular-level response. Clinical trials exploring innovative approaches, such as combining hypomethylation agents that target epigenetic regulators, drugs proven effective in myelodysplastic syndrome, or immune and inflammatory modulators with JAK inhibitors, have demonstrated promising results. These combinations may be more effective in patients with high-risk mutations and complex mutation profiles. Expanding mutation profiling studies with more sensitive and specific molecular methods, as well as sequencing a broader spectrum of genes in clinical patients, may reveal molecular mechanisms in cases currently lacking detectable driver mutations, provide a better understanding of the association between genetic alterations and clinical phenotypes, and offer valuable information to advance personalized treatment protocols to improve long-term survival and eradicate mutant clones with the hope of curing MF.