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

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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Ajax Therapeutics Announces FDA Clearance of IND Application for AJ1-11095, a First-in-Class Type II JAK2 inhibitor, for the Treatment of Myelofibrosis

– AJ1-11095 is the first Type II JAK2 Inhibitor to ever enter the clinic 

– Phase 1 dose escalation study expected to begin in 2H 2024 –

NEW YORK & CAMBRIDGE, Mass.–(BUSINESS WIRE)–Ajax Therapeutics, Inc., a biopharmaceutical company developing next generation JAK inhibitors for patients with myeloproliferative neoplasms (MPNs), today announced that it has received clearance for its Investigational New Drug (IND) application from the U.S. Food and Drug Administration (FDA) to initiate a Phase 1clinical study of AJ1‑11095, a first-in-class Type II JAK2 inhibitor, for the treatment of patients with myelofibrosis.

“This is an important milestone for our company and our first program to enter the clinic and the first clinical study to ever evaluate a Type II JAK2 inhibitor in patients.”

“We are thrilled to obtain clearance to advance AJ1-11095 into the clinic and excited to bring this innovative new medicine to patients with myelofibrosis,” said Martin Vogelbaum, co-founder and CEO of Ajax Therapeutics. “This is an important milestone for our company and our first program to enter the clinic and the first clinical study to ever evaluate a Type II JAK2 inhibitor in patients.”

“We look forward to the clinical development of AJ1-11095 in myelofibrosis and to initiating our Phase 1 dose escalation study, AJX-101, later this year,” said David Steensma, MD, FACP, Chief Medical Officer at Ajax. “As a first-in-class therapy with a unique mechanism as a Type II inhibitor of JAK2, AJ1-11095 was developed to provide a much-needed new treatment for patients with myelofibrosis by offering the potential for improved efficacy with disease modifying effects compared to existing therapies.”

About AJ1-11095

AJ1-11095 was designed by Ajax, through our collaboration with Schrödinger, to be a next generation JAK2 inhibitor by using structure-based drug design and computational methods at scale to selectively bind the Type II conformation of the JAK2 kinase and to provide greater efficacy with disease modification compared to all currently approved JAK2 inhibitors which bind the Type I conformation of JAK2. Additionally, AJ1-11095 has been shown in preclinical studies to reverse marrow fibrosis, reduce mutant allele burden and maintain efficacy against MPN cells that become resistant to chronic Type I JAK2 inhibition.

About Myelofibrosis

Myelofibrosis (MF) is a rare blood cancer that affects approximately 20,000 patients in the United States. The disease is characterized by spleen enlargement, scarring (fibrosis) in the bone marrow, progressive anemia, and debilitating symptoms, such as fatigue, night sweats, itching, and abdominal discomfort, which can impair a patient’s’ quality of life. The most widely used treatment for MF patients are Type I JAK2 inhibitors which can reduce spleen size and provide symptomatic improvement but have little effect on the underlying cause of disease. Over time, most MF patients stop Type I JAK2 inhibitor therapy. The most common causes for treatment discontinuation include a lack of benefit or loss of response, adverse events, and disease progression, leaving significant unmet treatment needs for these patients.

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Novel Targets Beyond the JAK-STAT Pathway Aim to Push Myelofibrosis Treatment Forward

Jax DiEugenio

Ongoing research in myelofibrosis continues to focus on agents directed at novel targets with the hope of expanding treatment options beyond the host of JAK inhibitors used in this treatment paradigm, according to Anthony M. Hunter, MD.

“[There are] a lot of novel agents on the horizon [that could] work in combination with JAK inhibitors to hopefully continue to move that bar forward for patients [with myelofibrosis,” said Hunter, who is an assistant professor in the Department of Hematology and Medical Oncology at Emory University School of Medicine and the medical director of the Immediate Care Center at Winship Cancer Institute of Emory University in Atlanta, Georgia.

In an interview with OncLive®, Hunter explained the evolving understanding of the biology of myelofibrosis, detailed the growth of JAK inhibitors being used for the treatment of these patients, and expanded on novel targets and agents currently being tested in clinical trials.

OncLive: How has our understanding of the pathology of myelofibrosis evolved in recent years as more research studies have been conducted?

Hunter: What has been well documented for years now is that the key biologic pathway or cell-signaling pathway actually involved in myeloproliferative neoplasms [MPN] or myelofibrosis is the JAK-STAT pathway. That [understanding] was advanced in 2005 when we found out about the JAK2 mutation in a large percentage of these patients, [and we] subsequently [found out about] the MPL and CALR mutations, as well. We find that in all patients with MPN or myelofibrosis, irrespective of those mutations, we see activation of this JAK-STAT signaling pathway, which has a lot of different effects and we can break those up into effects on hematopoiesis, or how they affect sort of blood cell production.

Then we also see increases in inflammatory cytokine signaling. The JAK/STAT pathway signals through a lot of cytokine and inflammatory receptors, so we see a lot of inflammatory signaling increase in a number of different cytokine levels and in myelofibrosis, which impacts the disease and the symptoms that we see. That has been key to [understanding] the biology [of myelofibrosis] and has led to the development of JAK inhibitors.

We’ve started to move beyond [the JAK-STAT] pathway a little bit, as well. A lot of the research now and new agents that are being explored in clinical trials are largely looking at non–JAK inhibitor agents, combining other pathways such as BET inhibitors, various other signaling molecules, and anti-fibrotic type compounds. All of those have additional roles, along with the JAK-STAT pathway in myelofibrosis.

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Momelotinib Improves Anemia in JAK Inhibitor-Naive Myelofibrosis

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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Serum Albumin Levels May Predict Survival Among Patients With Myelofibrosis Treated With Ruxolitinib

Serum albumin may function as a dynamic surrogate marker for clinical outcomes among patients with myelofibrosis treated with ruxolitinib, according to research published in JCO Precision Oncology. The utility of this surrogate measure may, however, vary by a given patient’s treatment status.

Previous work has established ruxolitinib, a JAK inhibitor, as a standard of care among patients with myelofibrosis. Yet although this treatment may help to reduce spleen size and symptom burden, it is unclear whether it improves overall survival (OS) rates.

New models, such as the RR6 model, have aimed to provide a prognostic surrogate measure for OS, though whether these models effectively distinguish high-risk disease from cases where there is no response to treatment is unclear. For this study, researchers aimed to evaluate whether serum albumin — which is linked with an anti-inflammatory response to treatment — is an effective surrogate marker for OS among patients with myelofibrosis.

Overall, data from 396 patients were included. In the cohort, among evaluable patients, 91 had received ruxolitinib while 305 were naïve to treatment, 58% of patients were male sex, and 72% of patients had primary myelofibrosis.

Analysis suggested that serum albumin levels frequently dropped among all patients, though this was less pronounced among patients treated with ruxolitinib. Relatedly, patients with a high serum albumin level at baseline had improved median OS periods (53.5 months) compared to patients with low levels (29.8 months; odds ratio, 1.95; <.001).

The link between serum albumin levels and OS was independent of variables included in the dynamic international prognostic scoring system, though only among patients who were naïve to ruxolitinib.

Future efforts to incorporate serum albumin with other inflammatory markers into an inflammatory index and assess its relevance in the context of other JAK inhibitors and combinations are ongoing.

Furthermore, among patients treated with ruxolitinib, changes in serum albumin levels predicted OS. Among patients with stable levels or an increase, median OS was 82.7 months, compared with 64.1 months among patients with a decrease (=.04).

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Genetics and Genetic Testing to Inform Myelofibrosis Clinical Management

by Charles Bankhead, Senior Editor, MedPage Today 

The history of primary myelofibrosis dates back to 1951 and the description of four distinct clinicopathologic entitiesopens in a new tab or window that came to be known as myeloproliferative neoplasms (MPNs): chronic myeloid leukemia (CML), polycythemia vera, essential thrombocythemia, and myelofibrosis.

Discovery of the Philadelphia (Ph) chromosome in 1960opens in a new tab or window paved the way to identification of BCR/ABL as the principal genetic driver of CML. Another 45 years passed before the discovery of a first genetic driver of non-Ph MPNs, a mutation in the Janus kinase 2 (JAK2) gene,opens in a new tab or window which occurs in 50-60% of myelofibrosis cases.

“The identification of that particular pathway was foundational, and it has changed the face of how we treat patients,” said James Rossetti, DO, of the University of Pittsburgh. “The JAK2 mutation is not present in everyone with myelofibrosis, and there are other mutations as well.”

Researchers identified a third key driver in 2013opens in a new tab or window: calreticulin gene (CALR). The mutation is associated with about 25% of myelofibrosis cases.

Most studies have shown that JAK2MPL, and CALR are mutually exclusiveopens in a new tab or window and do not occur together. However, a few studies have shown co-occurrence of the three key mutations. Even though JAK2MPL, and CALR usually do not occur together, numerous other mutations have been identified in association with the three primary mutations. As many as 80% of patients with myelofibrosisopens in a new tab or window have one or more other mutations.

Historically, myelofibrosis treatment was palliative in nature, aimed at relieving specific symptoms. The discovery of the JAK2 driver mutation has transformed treatment. Since 2011 four JAK2 inhibitors have received FDA approval: ruxolitinib (Jakafi)opens in a new tab or window, fedratinibopens in a new tab or window (Inrebic), pacritinibopens in a new tab or window (Vonjo), and momelotinibopens in a new tab or window (Ojjaara). All four drugs demonstrated ability to reduce splenomegaly, a major clinical manifestation of myelofibrosis, as well as symptoms.

Some of the co-occurring mutations are targetable, creating interest in combination therapies that simultaneously target different signaling pathways, said Aaron Gerds, MD, of the Cleveland Clinic. One such combination was evaluated in a clinical trial that paired a JAK2 inhibitor with an IDH2 inhibitor.

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A Grand Time in Grand Rapids

MPN Advocacy & Education International held an in-person patient/caregiver event in Grand Rapids, Michigan on April 25th. The room buzzed with excitement and camaraderie as patients and caregivers had the opportunity to engage with each other and MPN experts on a wide range of topics. 

Dr. Anas Al-Janadi gave an overview of the history of MPNs and defined where we are in our current understanding of the disease and what the future may hold. While exciting discoveries were made that supported the development of drug therapies for MPN patients; such as the JAK2 mutation in 2005 and later the MPL and CALR mutations, the MPN community is still working to better understand the reasons for disease progression and ways to reduce symptom burden.

Dr. Kristin Pettit, on the heels of her wedding (Congrats, Dr. Pettit), discussed the challenges MPN patients have flying, having elective or emergency surgeries, symptom management, and some critical women’s issues. Each topic had the following take-aways: check with your doctor and practice good self-care. Dr. Pettit emphasized hydration, healthy eating, exercise and reducing stress.

Dr. Aaron Gerds shared a play-by-play of diagnosing and treating MPNs. He began by situating ET, PV, and MF on the greater spectrum of Myeloid Neoplasms. Dr. Gerds, along with the other experts that presented, stressed the importance of a good clinical examination including a thorough history and a hands-on physical examination. Gerds went on to describe the testing required to make a proper MPN diagnosis, such as; blood counts, chemistries, infectious disease, bone marrow biopsy, and molecular testing. Afterwards, he walked us through the process of navigating individual risk and treatment options using the National Comprehensive Cancer Network (NCCN) Guidelines for Myelofibrosis. 

Justin Grinell, owner and head trainer of State of Fitness, reminded us that our health is not our fault, but it is our responsibility. He shared some ways to move toward a healthy lifestyle by incorporating an 11 min movement break in our day. To take just 11 minutes each day doing something active at your own Zone 2 (when your heart rate is 180 minus your age) can have an accumulative positive effect on not just your body but on your brain as well. Be sure to look for Justin this summer during our Healthy Summer Series webinars where you can join Justin for a quick lunch-time workout. 

Finally, Dr. Craig Kessler implored patients to ask questions. Ask your doctor questions about the treatment plan they create for you. Ask what component of MPN symptoms they are focusing on, and how the treatment they recommend will address that component (anemia, blood counts, spleen reduction, etc.). He stressed getting your COVID-19 vaccine and boosters. He also made clear that your questions matter and not to be afraid to ask.

We want to thank the specialists for sharing their valuable information and spending their time away from their respective institutions. We also want to thank our patients and their family members and friends for joining us and asking such thought-provoking questions. We hope that you will have a chance to join us at our next MPN Advocacy and Education International in-person event in Asheville, NC on Thursday August 22nd. To learn more, please visit www.mpnadvocacy.com/events-list.

Dr Sekeres on the Rationale for the FDA Approval of Momelotinib in Myelofibrosis

Mikkael A. Sekeres, MD, MS

Mikkael A. Sekeres, MD, MS, professor, medicine, chief, Division of Hematology, Leukemia Section, the University of Miami Health System, Sylvester Comprehensive Cancer Center, discusses the background on the FDA approval of momelotinib (Ojjaara) for the treatment of patients with anemic myelofibrosis.

At a recent OncLive® State of the Science Summit™ on hematologic malignancies, Sekeres and colleagues provided updates in the realm of myelodysplastic syndromes. Notably, one of these updates includes the FDA approval of momelotinib for the treatment of adult patients with intermediate or high-risk myelofibrosis with anemia. Originally, the phase 3 SIMPLIFY-1 (NCT01969838) and SIMPLIFY-2 (NCT02101268) trials investigated momelotinib compared with ruxolitinib (Jakafi) and momelotinib compared with best available therapy, respectively, Sekeres begins. In SIMPLIFY-2, although patients receiving momelotinib didn’t show a significant improvement in spleen response, they experienced a notable enhancement in symptom score, a benefit that is crucial for patients with myelofibrosis, he reports.

Subsequently, the phase 3 MOMENTUM trial (NCT04173494) was initiated, randomly assigning symptomatic patients with myelofibrosis in a 2:1 ratio to receive either momelotinib or danazol. Notably, significant improvement in symptom scores was observed with momelotinib, Sekeres states, saying that furthermore, substantial improvement in spleen size reduction was noted, forming the basis for momelotinib’s FDA approval. Additionally, there was a trend toward enhanced red blood cell transfusion independence rates among patients, Sekeres adds.

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Connecting Spleen Volume Reduction to Survival Outcomes in MF

Targeted Oncology Staff

CASE SUMMARY

A 68-year-old woman presented to her physician with symptoms of mild fatigue. Her spleen was palpable 6-7 cm below the left costal margin​, but she had no known comorbidities. Next-generation sequencing revealed a JAK2 V617F mutation​, and her karyotype was46XX.​ A bone marrow biopsy showed megakaryocyte proliferation and atypia with evidence of reticulin fibrosis​, and a blood smear was positive for leukoerythroblastosis​.

Her laboratory values also led to a diagnosis of primary myelofibrosis (MF). Risk stratification based on the dynamic international prognostic scoring system gave her a score of intermediate-1, and based on the mutation-enhanced international prognostic score system for transplantation-age she was also determined to be at intermediate risk​.

DISCUSSION QUESTIONS

  • Did the overall survival data from the COMFORT-I trial (NCT00952289) and COMFORT-II trial (NCT00934544) impact the way you manage patients with MF?​
  • How do you monitor and manage anemia in patients with primary MF prior to starting Janus kinase (JAK) inhibitor therapy?​

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How the PERSIST-2 Results Show The Benefit of Pacritinib in MF

Targeted Oncology Staff

Targeted OncologyWhat was the make-up of the PERSIST-2 trial (NCT02055781) looking at pacritinib (Vonjo) in patients with myelofibrosis (MF)?

JOHN MASCARENHAS, MD: This was the more interesting of the 2 PERSIST studies. PERSIST-2 looked at patients with platelets of 100,000/µL or less.1 So, the cytopenic patient with MF could have been given a Janus kinase [JAK] inhibitor before being enrolled, and half did in this study…but these are patients that were hard to treat, which was opposite to the set-up of the COMFORT-1 [NCT00952289] and COMFORT-2 [NCT00934544] studies.2 [Patients in PERSIST-2 study] were given either 400 mg daily or 200 mg of twice daily pacritinib vs patients on best available therapy [BAT], which could also include ruxolitinib [Jakafi], with a coprimary end point of spleen volume reduction of 35% or more and reduction of the total symptom score at week 24.1

What stood out among patients enrolled in either arm of the study?

I think what’s important to appreciate is when asking the investigator what they would give to patients who were randomly assigned to the BAT arm is that there is a lack of options available. In the BAT arm, 45% of patients got low-dose ruxolitinib, 19% had no options, while some patients were getting hydroxyurea [19%], steroids [13%], and even interferons [2%], which I would argue don’t work in this setting.1 These were patients who had higher-risk disease, and half of them had hemoglobin counts less than 10 g/dL, and the median platelet count was somewhere around 50,000/µL [in a majority of patients in both arms].

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