Safety evaluation of ruxolitinib for treating myelofibrosis

Current therapies for classic myeloproliferative neoplasms: A focus on pathophysiology and supportive care

PURPOSE

This article concisely evaluates current therapies that have received regulatory approval for the treatment of classic myeloproliferative neoplasms (MPNs). Pertinent pathophysiology and supportive care are discussed. Emerging therapies are also briefly described.

SUMMARY

MPNs are a heterogeneous group of diseases characterized by acquired abnormalities of hematopoietic stem cells (HSCs), resulting in the generation of transformed myeloid progenitor cells that overproduce mature and immature cells within the myeloid lineage. Mutations in JAK2 and other driver oncogenes are central to the genetic variability of these diseases. Cytoreductive therapies such as hydroxyurea, anagrelide, interferon, and therapeutic phlebotomy aim to lower the risk of thrombotic events without exposing patients to an increased risk of leukemic transformation. However, no comparisons can be made between these therapies, as reduction of thrombotic risk has not been used as an endpoint. On the other hand, Janus kinase (JAK) inhibitors such as ruxolitinib, fedratinib, pacritinib, and momelotinib (an investigational agent at the time of writing) directly target the constitutively activated JAK-signal transducer and activator of transcription (JAK-STAT) pathway of HSCs in the bone marrow. Mutations of genes in the JAK-STAT signaling pathway provide a unifying understanding of MPNs, spur therapeutic innovations, and represent opportunities for pharmacists to optimize mitigation strategies for both disease-related and treatment-related adverse effects.

CONCLUSION

Treatment options for MPNs span a wide range of disease mechanisms. The growth of targeted therapies holds promise for expanding the treatment arsenal for these rare, yet complex diseases and creates opportunities to optimize supportive care for affected patients.

Pharmacokinetics and Pharmacodynamics of Ruxolitinib: A Review

BACKGROUND AND OBJECTIVE

Ruxolitinib is a tyrosine kinase inhibitor targeting the Janus kinase (JAK) and signal transducer and activator of transcription (STAT) pathways. Ruxolitinib is used to treat myelofibrosis, polycythemia vera and steroid-refractory graft-versus-host disease in the setting of allogeneic stem-cell transplantation. This review describes the pharmacokinetics and pharmacodynamics of ruxolitinib.

METHODS

Pubmed, EMBASE, Cochrane Library and web of Science were searched from the time of database inception to march 15, 2021 and was repeated on November 16, 2021. Articles not written in English, animal or in vitro studies, letters to the editor, case reports, where ruxolitinib was not used for hematological diseases or not available as full text were excluded.

RESULTS

Ruxolitinib is well absorbed, has 95% bio-availability, and is bound to albumin for 97%. Ruxolitinib pharmacokinetics can be described with a two-compartment model and linear elimination. Volume of distribution differs between men and women, likely related to bodyweight differences. Metabolism is mainly hepatic via CYP3A4 and can be altered by CYP3A4 inducers and inhibitors. The major metabolites of ruxolitinib are pharmacologically active. The main route of elimination of ruxolitinib metabolites is renal. Liver and renal dysfunction affect some of the pharmacokinetic variables and require dose reductions. Model-informed precision dosing might be a way to further optimize and individualize ruxolitinib treatment, but is not yet advised for routine care due to lack of information on target concentrations.

CONCLUSION

Further research is needed to explain the interindividual variability of the ruxolitinib pharmacokinetic variables and to optimize individual treatment.

Light and shade of ruxolitinib: positive role of early treatment with ruxolitinib and ruxolitinib withdrawal syndrome in patients with myelofibrosis

INTRODUCTION

Myelofibrosis (MF) is characterized by ineffective and hepatosplenic extramedullary hematopoiesis due to fibrotic changes in the bone marrow and systemic manifestations due to aberrant cytokine release. Ruxolitinib (RUX) is the first JAK1/JAK2 inhibitor that is clinically approved to treat splenomegaly by ameliorating inflammatory cytokines and myeloproliferation in MF.

AREAS COVERED

Patients with less advanced MF may also achieve better outcome and successful treatment with RUX. However, approximately 40% of the patients failed to achieve a stable response or have shown to be intolerant to RUX, and most of them discontinued RUX. In patients who need to discontinue or reduce the dose of RUX for any reason, RUX is known to induce a paradoxical accumulation of JAK activation loop phosphorylation that is causing RUX discontinuation syndrome (RDS). To review the topic of MF and RUX, we searched relevant literatures using PubMed.

EXPERT OPINION

RUX treatment in lower IPSS risk patients who present with splenomegaly and disease-associated symptoms can be helpful. A careful discontinuation strategy with steroids may reduce the probability of RDS, and the recognition of RDS with early re-introduction of RUX is important in the treatment of severe cases of RDS.

New Horizons in Myeloproliferative Neoplasms Treatment: A Review of Current and Future Therapeutic Options

Philadelphia-negative myeloproliferative neoplasms (MPN) are aggressive diseases characterized by clonal proliferation of myeloid stem cells. The clonal process leads to excessive red cells production, platelets production, and bone marrow fibrosis. According to the phenotype, MPN can be classified as polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF). MPN patients have shortened survival due to the increased risk of thrombosis, hemorrhages, and transformation to acute myeloid leukemia (AML). Prognosis is variable, with a shorter life expectancy in myelofibrosis. Currently, drug therapy can reduce symptoms, splenomegaly, and risk of thrombosis. Still, some patients can be resistant or intolerant to the treatment. At the same time, allogeneic stem cell transplant (ASCT) is the only treatment modality with the potential to cure the disease. Nevertheless, the ASCT is reserved for high-risk leukemic progression patients due to the risk of treatment-related death and comorbidity. Therefore, there is a need for new drugs that can eradicate clonal hematopoiesis and prevent progression to more aggressive myeloid neoplasms. Thanks to the better understanding of the disease’s molecular pathogenesis, many new potentially disease-modifying drugs have been developed and are currently in clinical trials. This review explores the most promising new drugs currently in clinical trials.

Posterior Reversible Encephalopathy Syndrome (PRES) in a Patient With Primary Myelofibrosis on Ruxolitinib

Posterior reversible encephalopathy syndrome (PRES) is a reversible neurological syndrome characterized by headache, seizures, altered mental status, and visual abnormalities, in association with the characteristic bilateral white matter abnormalities in the posterior cerebral hemispheres. As the name suggests, it is typically reversible with clinical recovery within a few days, while the magnetic resonance imaging (MRI) abnormalities resolve much more slowly. We present a 78-year-old female with a known diagnosis of primary myelofibrosis (PMF), on ruxolitinib, a Janus kinase (JAK) 1 and 2 inhibitor, presenting with altered mental status. On presentation, she was hypertensive and with possible sepsis, secondary to urinary tract infection (UTI). She was intubated because of her low Glasgow Coma Scale (GCS), to secure her airways. Computed tomography (CT) of the brain did not reveal any acute ischemic changes. MRI of the brain exhibited findings suggestive of PRES. Ruxolitinib was held and the patient was treated with antihypertensives, anticonvulsants, and antibiotics. Within 24 hours of hospitalization, the patient had a complete neurological recovery, which is diagnostic of PRES. She was extubated successfully and was discharged with a resolution of her symptoms. Although several chemotherapeutic and immunosuppressant drugs are reported to be associated with PRES, the association between ruxolitinib and PRES has not been well established. Thus, case reporting is important to highlight the possible association between ruxolitinib and PRES.

JAK Inhibition for the Treatment of Myelofibrosis: Limitations and Future Perspectives

The 2011 approval of ruxolitinib ushered in the Janus kinase (JAK) inhibitor era in the treatment of myelofibrosis (MF), and 2019 saw the US approval of fedratinib. The first therapeutic agents approved by regulatory authorities for MF, these drugs attenuate the overactive JAK-signal transducer and activator of transcription (STAT) signaling universally present in these patients, translating into major clinical benefits in terms of spleen shrinkage and symptom improvement. These, in turn, confer a survival advantage on patients with advanced disease, demonstrated in the case of ruxolitinib, for which long-term follow-up data are available. However, JAK inhibitors do not improve cytopenias in most patients, have relatively modest effects on bone marrow fibrosis and driver mutation allele burden, and clinical resistance eventually develops. Furthermore, they do not modify the risk of transformation to blast phase; indeed, their mechanism of action may be more anti-inflammatory than truly disease-modifying. This has spurred interest in rational combinations of JAK inhibitors with other agents that may improve cytopenias and drugs that could potentially modify the natural history of MF. Newer JAK inhibitors that are distinguished from ruxolitinib and fedratinib by their ability to improve anemia (eg, momelotinib) or safety and efficacy in severely thrombocytopenic patients (eg, pacritinib) are in phase 3 clinical trials. There is also interest in developing inhibitors that are highly selective for mutant JAK2, as well as "type II" JAK2 inhibitors. Overall, although current JAK inhibitors have limitations, they will likely continue to form the backbone of MF therapy for the foreseeable future.

Life after ruxolitinib: Reasons for discontinuation, impact of disease phase, and outcomes in 218 patients with myelofibrosis

BACKGROUND

After discontinuing ruxolitinib, the outcome of patients with myelofibrosis reportedly has been poor. The authors investigated whether disease characteristics before the receipt of ruxolitinib may predict drug discontinuation in patients with myelofibrosis and whether reasons for drug discontinuation, disease phase at discontinuation, and salvage therapies may influence the outcome.

METHODS

A centralized electronic clinical database was created in 20 European hematology centers, including clinical and laboratory data for 524 patients who received ruxolitinib for myelofibrosis.

RESULTS

At 3 years, 40.8% of patients had stopped ruxolitinib. Baseline predictors of drug discontinuation were: intermediate-2-risk/high-risk category (Dynamic International Prognostic Score System), a platelet count <100 ×10⁹ per liter, transfusion dependency, and unfavorable karyotype. At last contact, 268 patients (51.1%) had discontinued therapy, and the median drug exposure was 17.5 months. Fifty patients (18.7%) died while taking ruxolitinib. The reasons for discontinuation in the remaining 218 patients were the lack (22.9%) or loss (11.9%) of a spleen response, ruxolitinib-related adverse events (27.5%), progression to blast phase (23.4%), ruxolitinib-unrelated adverse events (9.2%), and allogeneic transplantation during response (5.1%). The median survival after ruxolitinib was 13.2 months and was significantly better in the 167 patients who discontinued ruxolitinib in chronic phase (27.5 vs 3.9 months for those who discontinued in blast phase; P < .001). No survival differences were observed among patients who discontinued ruxolitinib in chronic phase because of lack of response, loss of response, or ruxolitinib-related adverse events. The use of investigational agents and/or ruxolitinib rechallenge were associated with improved outcome.

CONCLUSIONS

The survival of patients with myelofibrosis after discontinuation of ruxolitinib is poor, particularly for those who discontinue in blast phase. Salvage therapies can improve outcome, emphasizing the need for novel therapies.

Fungal Infections with Ibrutinib and Other Small-Molecule Kinase Inhibitors

Purpose of review

Small molecule kinase inhibitors (SMKIs) have revolutionized the management of malignant and autoimmune disorders. Emerging clinical reports point toward an increased risk for invasive fungal infections (IFIs) in patients treated with certain SMKIs. In this mini-review, we highlight representative examples of SMKIs that have been associated with or are expected to give rise to IFIs.

Recent findings

The clinical use of the Bruton's tyrosine kinase inhibitor ibrutinib as well as other FDA-approved SMKIs has been associated with IFIs. The fungal infection susceptibility associated with the clinical use of certain SMKIs underscores their detrimental effects on innate and adaptive antifungal immune responses.

Summary

The unprecedented development and clinical use of SMKIs is expected to give rise to an expansion of iatrogenic immunosuppressive factors predisposing to IFIs (and other opportunistic infections). Beyond increased clinical surveillance, better understanding of the pathogenesis of SMKI-associated immune dysregulation should help devising improved risk stratification and prophylaxis strategies in vulnerable patients.

The Implications of Liver Biopsy Results in Patients with Myeloproliferative Neoplasms Being Treated with Ruxolitinib

Ruxolitinib is increasingly being utilized for the treatment of myelofibrosis and polycythemia vera, but the potential for hepatic toxicity is poorly understood. We performed a retrospective review of hepatic damage occurring in patients with myeloproliferative neoplasms receiving ruxolitinib. Relevant histologic images of liver biopsies were reviewed by an experienced liver pathologist and reported to a multidisciplinary team including hepatology and hematology. A variety of liver pathology was observed including extramedullary hematopoiesis, obliterative portal venopathy, and drug-induced liver injury. In all cases reviewed, the liver biopsy had significant treatment implications. We conclude that hepatology referral and liver biopsy in patients receiving ruxolitinib therapy with biochemical evidence of liver injury reveals a variety of etiologies which have significant treatment impact. Clinicians should be aware of the potential causes of liver damage in this population and initiate prompt referral and liver biopsy.

Role of janus kinase inhibitors in the treatment of alopecia areata

Alopecia areata (AA) is a common hair loss disorder worldwide with characteristic exclamation mark hairs. Although AA is self-limited, it can last for several months or even years in some patients. Currently, there is no US Food and Drug Administration-approved treatment for AA. Many off-label treatments are available but with limited efficacy. Through a better understanding of molecular biology, many targeted therapies have emerged as new alternatives for various autoimmune diseases. Various janus kinase (JAK) and signal transducer and activator of transcription (STAT) proteins form signaling pathways, which transmit extracellular cytokine signals to the nucleus and induce DNA transcriptions. By inhibiting JAK, T-cell-mediated inflammatory responses are suppressed. Increasing evidence suggests that JAK inhibitors (JAKis) are effective in the treatment of many autoimmune diseases, including AA. Among these, several studies on tofacitinib, ruxolitinib, and baricitinib in AA had been published, demonstrating promising outcomes of these agents. Unlike oral formulations, efficacy of topical forms of tofacitinib and ruxolitinib reported in these studies is still unsatisfactory and requires improvement. This review aims to summarize evidence of the efficacy and safety of JAKis in the treatment of AA.

Ruxolitinib for the Treatment of Essential Thrombocythemia

Deregulated Janus Kinase 2 (JAK2) activation is central to the pathogenesis of most myeloproliferative neoplasms (MPNs), of which essential thrombocythemia (ET) is the most common entity. Patients with ET are risk-stratified according to their risk of thrombo-hemorrhagic complications. High-risk patients are offered treatments to reduce their platelet count using cytoreductive therapy. The disease course is often long and therapy intolerance is not infrequent. Ruxolitinib, a Janus Kinase (JAK) 1/JAK2 inhibitor, has demonstrated efficacy in patients with both myelofibrosis (MF) and polycythemia vera and is well tolerated. Side effects include predictable cytopenias and an augmented risk of infections. Ruxolitinib has been investigated in a small group of ET patients who were refractory/intolerant to hydroxycarbamide (HC) and demonstrated improvements in both symptoms and splenomegaly. Of note, a proportion of treated patients (13.2%) also had a significant reduction in platelet counts. However, these results require further validation in comparison with conventional therapy. Recently, a randomized-controlled phase 2 study (MAJIC-ET) assessed the role of Ruxolitinib in patients refractory or intolerant to HC. This study revealed that Ruxolitinib demonstrated some clinical efficacy but was only superior in terms of symptom control. In clinical practice, some individuals with ET do exhaust all potential treatment options and there may well be a role for Ruxolitinib in such patients or those with a significant symptom burden. However, in the wider context the goal of therapy with the use of JAK inhibitor therapy in ET needs to be defined carefully and we explore this within this timely review article.

An updated review of the JAK1/2 inhibitor (ruxolitinib) in the Philadelphia-negative myeloproliferative neoplasms

Ruxolitinib (Rux), a JAK1/2 inhibitor, has been approved for patients with myelofibrosis and in polycythemia vera with inadequate response/intolerance to hydroxycarbamide. Studies have demonstrated that Rux improves disease-related symptoms and splenomegaly. A late emerging observation from two Phase III trials was that Rux was associated with survival advantage in comparison with placebo or other available therapies in myelofibrosis. Important data suggest that for polycythemia vera Rux improved control of blood counts. Main hematological side effects are anemia and thrombocytopenia predominantly at the beginning of the treatment. Some studies and case reports highlighted potential risks of nonmelanoma skin cancers and increased risk of infection including reactivation of hepatitis B, tuberculosis or herpes zoster infections after Rux treatment.

Vitiligo Pathogenesis and Emerging Treatments

The pathogenesis of vitiligo involves interplay between intrinsic and extrinsic melanocyte defects, innate immune inflammation, and T-cell-mediated melanocyte destruction. The goal of treatment is to not only halt disease progression but also promote repigmentation through melanocyte regeneration, proliferation, and migration. Treatment strategies that address all aspects of disease pathogenesis and repigmentation are likely to have greatest efficacy, a strategy that may require combination therapies. Current treatments generally involve nontargeted suppression of autoimmunity, whereas emerging treatments are likely to use a more targeted approach based on in-depth understanding of disease pathogenesis, which may provide higher efficacy with a good safety profile.

JAK inhibitors in dermatology: The promise of a new drug class

New molecularly targeted therapeutics are changing dermatologic therapy. Janus kinase-signal transducer and activator of transcription (JAK-STAT) is an intracellular signaling pathway upon which many different proinflammatory signaling pathways converge. Numerous inflammatory dermatoses are driven by soluble inflammatory mediators, which rely on JAK-STAT signaling, and inhibition of this pathway using JAK inhibitors might be a useful therapeutic strategy for these diseases. Growing evidence suggests that JAK inhibitors are efficacious in atopic dermatitis, alopecia areata, psoriasis, and vitiligo. Additional evidence suggests that JAK inhibition might be broadly useful in dermatology, with early reports of efficacy in several other conditions. JAK inhibitors can be administered orally or used topically and represent a promising new class of medications. The use of JAK inhibitors in dermatology is reviewed here.

Experience with ruxolitinib in the treatment of polycythaemia vera

Polycythaemia vera (PV) is a myeloproliferative neoplasm classically characterized by an erythrocytosis and is associated with a high risk of thromboembolic events, constitutional symptoms burden and risk of transformation to myelofibrosis and acute myeloid leukaemia. Therapy is directed at the haematocrit (HCT) to reduce the risk of thrombotic events and usually comprises low-dose aspirin and phlebotomy to maintain HCT at >45%. Frequently in addition, cytoreductive therapy is indicated in high-risk patients for normalizing haematological parameters to mitigate the occurrence of thromboembolic events. Unfortunately, there is no clear evidence that current therapies reduce the risk of transformation to myelofibrosis and for some a risk of a therapy related complication is unknown for example leukaemia due to hydroxycarbamide (HC). First-line therapy for treating PV remains HC or interferon, the latter most often in younger patients, especially those of childbearing age. However, therapy related intolerance or resistance is a common feature and results in limited treatment options for such patients. The discovery of the JAK2 V617F mutation and consequently targeted therapy with Janus kinase inhibitors, in particular ruxolitinib, has extended the spectrum of agents that can be used as second or third line in PV. The findings of the phase II trial RESPONSE and the preliminary data from RESPONSE 2 trial have identified a role for ruxolitinib in PV patients who are resistant or intolerant to HC. In this article, using clinical cases we demonstrate our experience with ruxolitinib highlighting the clinical benefits and limitations we encountered in clinical practice.

Ruxolitinib for symptom control in patients with chronic lymphocytic leukaemia: a single-group, phase 2 trial

Background

Disease-related symptoms impair the quality of life of countless patients with chronic lymphocytic leukemia (CLL) who do not require systemic therapy. Currently available therapies are not specifically aimed at symptom control. Because stimulation of the B-cell receptor activates Janus kinase (JAK)-2 in CLL cells and the JAK2 inhibitor ruxolitinib improves symptoms of patients with myelofibrosis, we hypothesized that ruxolitinib would improve disease-related symptoms in CLL patients.

Methods

Ruxolitinib (10 mg twice daily) was administered to symptomatic CLL patients who did not require systemic therapy for CLL. Scores on the brief fatigue inventory (BFI), CLL module of the MD Anderson symptom inventory (MDASI) and symptom-associated interference in daily activities (interference score; IS), were assessed prior to treatment and after 3 months of treatment. Plasma cytokine/chemokine levels were measured at baseline and at 3 months.

Findings

Forty-one CLL patients (25 untreated and 16 previously treated) were enrolled. Thirty-two (78%) of the participants experienced ≥20% reduction in the average BFI score or in the average MDASI score. 59% of the participants had ≥2 units reduction in worst fatigue score in 24 hours as assessed by the BFI. The mean percentage reductions in BFI, MDASI, and IS scores were >42% (p<0.0001). Improvements in the three symptom scores correlated with reductions in levels of IL-6, C-reactive protein, CXCL10, osteopontin, TNF-α, ICAM-1/CD54, VCAM-1/CD106, and beta-2 microglobulin. Furthermore, treatment with ruxolitinib increased and then decreased lymphocyte counts to baseline levels or lower. Grade 3/4 cytopenias were recorded in three patients.

Interpretation

In CLL patients, ruxolitinib significantly improved disease-related symptoms, reduced cytokine and chemokine levels, and increased and then decreased lymphocyte counts, likely through mobilization followed by apoptosis of CLL cells. Further studies aimed at testing the therapeutic efficacy of ruxolitinib in CLL are warranted.

Funding

Supported by the Incyte Corp., MD Anderson Cancer Center Support Grant CA016672 and Award Number P01 CA049639 from the National Cancer Institute.

A comprehensive review of pacritinib in myelofibrosis

The first-in-class JAK1/JAK2 inhibitor ruxolitinib inhibits JAK/STAT signaling, inducing durable reductions in splenomegaly and constitutional symptoms in patients with myelofibrosis. However, the association of ruxolitinib therapy with myelosuppression indicates the continued need for optimal treatment choices in myelofibrosis. Pacritinib, a dual JAK2 and FLT3 inhibitor, improves disease-related symptoms and signs with manageable gastrointestinal toxicity in patients with myelofibrosis with splenomegaly and high-risk features, without causing overt myelosuppression, and therefore may provide an important treatment option for a range of patients with myelofibrosis. This article examines the role of JAK2 and FLT3 signaling in myelofibrosis and provides an overview of the clinical development of pacritinib as a new therapy for myelofibrosis.

JAK2 inhibition has different therapeutic effects according to myeloproliferative neoplasm development in mice

JAK2 inhibition therapy is used to treat patients suffering from myeloproliferative neoplasms (MPN). Conflicting data on this therapy are reported possibly linked to the types of inhibitors or disease type. Therefore, we decided to compare in mice the effect of a JAK2 inhibitor, Fedratinib, in MPN models of increasing severity: polycythemia vera (PV), post-PV myelofibrosis (PPMF) and rapid post-essential thrombocythemia MF (PTMF). The models were generated through JAK2 activation by the JAK2(V617F) mutation or MPL constant stimulation. JAK2 inhibition induced a correction of splenomegaly, leucocytosis and microcytosis in all three MPN models. However, the effects on fibrosis, osteosclerosis, granulocytosis, erythropoiesis or platelet counts varied according to the disease severity stage. Strikingly, complete blockade of fibrosis and osteosclerosis was observed in the PPMF model, linked to correction of MK hyper/dysplasia, but not in the PTMF model, suggesting that MF development may also become JAK2-independent. Interestingly, we originally found a decreased in the JAK2(V617F) allele burden in progenitor cells from the spleen but not in other cell types. Overall, this study shows that JAK2 inhibition has different effects according to disease phenotypes and can (i) normalize platelet counts, (ii) prevent the development of marrow fibrosis/osteosclerosis at an early stage and (iii) reduce splenomegaly through blockage of stem cell mobilization in the spleen.