Podoltsev Reviews JAK Inhibition Options for Patient With Primary Myelofibrosis

Peers & Perspectives in OncologyJune I 2024
Pages: 28

During a Case-Based Roundtable® event, Nikolai Podoltsev, MD, PhD, discussed appropriate JAK inhibitor therapy options for a 62-year-old patient with myelofibrosis who had potentially declining hemoglobin and platelet counts.

Nikolai Podoltsev, MD, PhD

Nikolai Podoltsev, MD, PhD

Associate Professor, Internal Medicine (Hematology)

Duffy Firm Chief for Education, Department of Internal Medicine

Associate Director, Hematology/Oncology Fellowship Program

Yale School of Medicine

New Haven, CT


  • A man aged 62 years presented to his primary care physician (PCP) with symptoms of fatigue, night sweats, and increased bruising.
  • Medical history: type 2 diabetes, hypercholesterolemia, and hypertension
  • The PCP noticed lower hemoglobin concentration (11.0-9.5 g/dL) and platelet count (350,000-195,000/μL) from a previous annual physical examination.
  • Two months post PCP visit, a hematologic oncologist saw the patient.
  • Examination findings: spleen 5 cm below left costal margin, fatigue and night sweats worsening, and bone pain
  • He had a history of squamous cell carcinoma of the skin.
  • Hemoglobin: 9.1 g/dL
  • Platelet count: 135,000/μL
  • Bone marrow fibrosis of grade 2/3, with less than 5% bone marrow blasts
  • Molecular analysis showed a JAK2 V617F mutation with normal karyotype and no additional mutations by next-generation sequencing.
  • Blood: 1% blasts by manual count/flow cytometry
  • ECOG performance status: 2
  • Diagnosis: primary myelofibrosis

PEERS & PERSPECTIVES IN ONCOLOGY™: Please discuss the Janus kinase (JAK) inhibitors available for treating this patient with primary myelofibrosis.

PODOLTSEV: There are 4 JAK inhibitors approved. Ruxolitinib [ Jakafi] has been out for more than 10 years, since 2011, and fedratinib [Inrebic] since 2019. Fedratinib is available and is a reasonable drug to use after ruxolitinib failure for patients with proliferative disease because it’s good at controlling the symptoms. But similar to ruxolitinib, it causes cytopenias, and that’s why it doesn’t have much of a role for patients with anemia and thrombocytopenia. We’re discussing a patient with cytopenic myelofibrosis. Then pacritinib [Vonjo] was approved in 2022 and momelotinib [Ojjaara] in 2023.

How does ruxolitinib fit into the myelofibrosis treatment landscape?

Ruxolitinib is the JAK inhibitor we’re all familiar with because it’s been in use for so long, [inhibiting] JAK1/2. You do not want to abruptly discontinue it because of ruxolitinib discontinuation syndrome with a lot of inflammatory symptoms, sepsis-like, and sometimes significant morbidity as well as mortality.

Two studies led to the approval of this JAK inhibitor in 2011, COMFORT-I and COMFORT-II [NCT00952289; NCT00934544].1,2 [Patients in] COMFORT-I were randomly assigned 1:1 vs… placebo, and the European COMFORT-II study was 2:1 with best available therapy [BAT].

In COMFORT-I, at 24 weeks there was significant reduction of spleen size.1 Specifically 35% reduction by imaging was seen in 42% of patients on ruxolitinib compared with less than 1% on placebo. COMFORT-II took the same parameter at 48 weeks, and here the number was a little less, 28% vs 0% with BAT.2

What other data are available for ruxolitinib?

[Results of another trial also showed] improved survival based on spleen response at 6 months and by durability of spleen response.3 We’re always looking for evidence of disease modification, and we’re talking about allele burden, degree of fibrosis, perhaps circulating CD34 cells, and clustering of megakaryocytes. But to me, spleen reduction may be one of those markers of modification of outcomes because if you can reduce the spleen, you can improve survival based on [ruxolitinib data].4,5 Also, we’re giving JAK inhibitors for control of symptoms and perhaps maybe improvement of anemia.

The combined data from COMFORT-I and COMFORT-II were a post hoc analysis of survival, and there was a difference in survival, even though the overwhelming majority of patients crossed over from placebo/BAT arms to ruxolitinib [arms].6 Those who were initially randomly assigned to ruxolitinib survived longer.

This is meta-analysis of 2 studies, but it showed a difference of 1.5 years of median survival between ruxolitinib and control groups when combined, 5.3 vs 3.8 years, respectively. We do not give this medication to improve survival; we give it for symptoms. But I mention this to patients, especially to those who have improved their spleen size, that I am expecting them to live longer.

The main adverse event [AE] of the JAK1/2 inhibitor ruxolitinib is hematologic. For anemia, [with ruxolitinib vs placebo in COMFORT-I, grade 3/4 AE rates were] 45% vs 19%.1 There was also thrombocytopenia and sometimes neutropenia. Anemia is certainly the more common problem among cytopenias for ruxolitinib use…. If you’re using ruxolitinib and patients become anemic, you still have improvement of symptoms and…spleen volume. So despite worsening counts, those patients may still benefit from this treatment, and some of them would accept, once in a while, transfusions for overall improved quality of life, which you can see with use of ruxolitinib.

What data for pacritinib are available in the myelofibrosis population?

For pacritinib, we have the PERSIST trials, and I’m going to specifically focus on PERSIST-2 [NCT02055781], which led to the approval of this JAK inhibitor.7 This study included patients with a platelet count of 100,000/μL or less. [It was] a first line for approximately a quarter of patients. PERSIST-2 randomly assigned patients to 3 groups: The first group received pacritinib 400 mg once daily, the second group received pacritinib 200 mg twice daily—and that was the best-performing group and that dose was approved by the FDA—and finally [the last group received] BAT. They measured spleen volume by imaging; 35% or higher spleen volume reduction [SVR] at week 24 and reduction by 50% of total symptom score [TSS] at week 24 [were] co–primary end points.

Most of those patients had intermediate-to high-risk disease. More than 50% had anemia with a hemoglobin level less than 10 g/dL. Forty-five percent of patients in the BAT arm were taking ruxolitinib.

How did patients with myelofibrosis receiving pacritinib do on PERSIST-2?

The primary end point of SVR of 35% was accomplished by 18% of patients in the pacritinib arms and only 3% of patients in the BAT arms. Patients with a low platelet count—less than 50,000/μL— also benefited from response at 29% with pacritinib for SVR by 35% and only 3% in the BAT group.

The TSS 50% reduction at week 24 was accomplished by 32% of patients using pacritinib twice a day and only 14% of patients with BAT, which was statistically significant [P = .01]. Looking at symptoms like fatigue, early satiety, abdominal discomfort, and such…pacritinib was a winner…in reduction of symptoms.

Some of the patients had improved hemoglobin levels… Transfusion dependence was reduced more significantly, especially among patients who were taking pacritinib 200 mg twice a day. Platelets are not fixed by this drug; they’re just staying stable. They were stable in patients who received treatment with the pacritinib 400 mg and pacritinib 200 mg twice a day.

[Furthermore, regarding] the PERSIST-2 data, because momelotinib was coming to the market, pacritinib [investigators] decided to look at the same type of parameter using the same criteria as for the momelotinib study in SIMPLIFY-1 [NCT01969838]. They looked at transfusion conversion rate and transfusion independence conversion rate.8 Among those who were transfusion dependent, 24% became transfusion independent when treated with pacritinib and only 5% when treated with BAT, and half of those patients were on ruxolitinib. Overall and in [subgroups of] patients who were not pretreated with ruxolitinib, those who had a platelet count less than 50,000/μL, and those with JAK2 allele burden less than 50% or more than 50%, there’s certainly [transfusion independence] benefit among patients who received pacritinib on the PERSIST-2 study.

What was the toxicity profile of pacritinib for these patients?

AEs seen in more than 10% of patients included diarrhea, nausea, and vomiting, which was a bit more common in this drug compared with BAT.7,9 But in general, it was reasonably well tolerated. There was a hold for the study related to cardiac toxicities—specifically QTc prolongation was concerning and then intracranial bleeding.9 But after reanalysis of data of the PERSIST-2 study, the hold was lifted and the drug was eventually approved at 200 mg twice a day.7

QTc may be important for this JAK inhibitor. There was concern about bleeding, but these were patients who at baseline had significant thrombocytopenia.

For the risk-adjusted AEs of interest…there were compared pooled data from PERSIST-2 and PAC-203 [PACIFICA; NCT03165734], which was mandated by the FDA before the drug approval to examine different doses and safety of pacritinib. Malignancy, excluding leukemic transformation, was more common in patients treated with BAT, specifically ruxolitinib. You cannot statistically compare them, but numerically the number is different. There was an increased risk of nonmelanoma skin cancer, which was more common in patients receiving ruxolitinib. Viral infections were also numerically more common with BAT, including zoster infections, and fungal infections were the same in both arms. These data are trying to make a point that perhaps pacritinib may be safer than ruxolitinib.

What other JAK inhibitors have been investigated for patients with myelofibrosis?

Momelotinib was approved in September 2023. In addition to inhibiting JAK1 and JAK2, it inhibits ACVR1…. Other than fedratinib, all the JAK inhibitors are approved for intermediate-1 through high-risk disease by DIPSS [Dynamic International Prognostic Scoring System] in patients who are symptomatic. With momelotinib, [investigators] specifically looked at patients who have anemia.10 The drug has certain drug interactions that you have to be mindful of, and the dose has to be adjusted in patients who have problems with liver function.

The MOMENTUM trial [NCT04173494] is the phase 3 study that led to the approval of the drug. This JAK inhibitor has 3 phase 3 studies: SIMPLIFY-1, SIMPLIFY-2 [NCT02101268], and MOMENTUM. But MOMENTUM was the one that led to the approval. Looking at the inclusion criteria, these were patients who progressed on a previous JAK inhibitor and had symptomatic myelofibrosis with TSS of 10 or more and anemia with a hemoglobin level less than 10 g/dL. They were randomly assigned 2:1, and the randomization was between momelotinib 200 mg daily plus placebo or danazol plus placebo. The study is criticized for selection of danazol as the comparator drug because danazol is not expected to improve spleen size or symptoms of patients, but it does help anemia, [though] not very frequently.

These patients were assessed at week 24 with the primary end point being reduction of TSS. How much of that you would expect with danazol was questionable to me. The secondary end point, though, included transfusion independence status at the end of week 24, looking at the previous 12 weeks before the end of this 24-week period, SVR at week 24, safety and survival, and patient-reported outcomes.

What results did investigators see with momelotinib?

Momelotinib was better than danazol in controlling patients’ symptoms.10 Now, from the standpoint of SVR, which was a secondary end point, momelotinib was better than danazol, but you would not expect danazol to shrink the spleen. For patients with SVR, the 35% reduction was 23% at the second-line treatment.

But the most interesting finding is the secondary end point of transfusion independence. A lot of the patients were transfusion dependent because only 13% in the momelotinib group and 15% in the danazol group were transfusion independent at baseline. The [momelotinib] increased independence from transfusion from 13% to 31%, so that is an 18% reduction, but still you have 70% of patients who are requiring transfusions at the end of 24 weeks. In the danazol group, the transfusion independence increased by 5%, from 15% to 20%. It was reasonable for danazol, which is not very effective, but nevertheless, there was some improvement of transfusion independence.

At 48 weeks, the rates improved.11 For momelotinib, TSS improved from 25% to 45%, transfusion independence from 30% to 57%, SVR of 35% or greater improved from 22% to 43%. In the danazol group, we also observed some response. But the reason is that after 24 weeks, those patients crossed over to momelotinib, so everyone was receiving momelotinib. It’s a decent drug, and it takes time to control symptoms on the spleen, but it does help with spleen and symptom control, as well as improving transfusion independence rates.

1. Verstovek S, Mesa RA, Gotlib J, et al. A double-blind, placebo-controlled trial of ruxolitinib for myelofibrosis. N Engl J Med. 2012;366(9):799-807. doi:10.1056/NEJMoa1110557
2. Harrison C, Kiladjian JJ, Al-Ali HK, et al. JAK inhibition with ruxolitinib versus best available therapy for myelofibrosis. N Engl J Med. 2012;366(9):787-798. doi:10.1056/NEJMoa1110556
3. Palandri F, Palumbo GA, Bonifacio M, et al. Durability of spleen response affects the outcome of ruxolitinib-treated patients with myelofibrosis: results from a multicentre study on 284 patients. Leuk Res. 2018;74:86-88. doi:10.1016/j.leukres.2018.10.001
4. Palandri F, Palumbo GA, Bonifacio M, et al. Baseline factors associated with response to ruxolitinib: an independent study on 408 patients with myelofibrosis. Oncotarget. 2017;8(45):79073-79086. doi:10.18632/oncotarget.18674
5. Menghrajani K, Boonstra PS, Mercer JA, et al. Predictive models for splenic response to JAK-inhibitor therapy in patients with myelofibrosis. Leuk Lymphoma. 2019;60(4):1036-1042. doi:10.1080/10428194.2018.1509315
6. Verstovsek S, Gotlib J, Mesa RA, et al. Long-term survival in patients treated with ruxolitinib for myelofibrosis: COMFORT-I and -II pooled analyses. J Hematol Oncol. 2017;10(1):156. doi:10.1186/s13045-017-0527-7
7. Mascarenhas J, Hoffman R, Talpaz M, et al. Pacritinib vs best available therapy, including ruxolitinib, in patients with myelofibrosis: a randomized clinical trial. JAMA Oncol. 2018;4(5):652-659. doi:10.1001/jamaoncol.2017.5818
8. Oh ST, Mesa RA, Harrison CN, et al. Pacritinib is a potent ACVR1 inhibitor with significant anemia benefit in patients with myelofibrosis. Blood Adv. 2023;7(19):5835-5842. doi:10.1182/bloodadvances.2023010151
9. Vonjo. Prescribing information. CTI BioPharma Corp; 2022. Accessed May 13, 2024. https://tinyurl.com/yfrx5pn7
10. Verstovsek S, Gerds AT, Vannucchi AM, et al. Momelotinib versus danazol in symptomatic patients with anaemia and myelofibrosis (MOMENTUM): results from an international, double-blind, randomised, controlled, phase 3 study. Lancet. 2023;401(10373):269-280. doi:10.1016/S0140-6736(22)02036-0
11. Gerds AT, Verstovsek S, Vannucchi AM, et al. Momelotinib versus danazol in symptomatic patients with anaemia and myelofibrosis previously treated with a JAK inhibitor (MOMENTUM): an updated analysis of an international, double-blind, randomised phase 3 study. Lancet Haematol. 2023;10(9):e735-e746. doi:10.1016/ S2352-3026(23)00174-6
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