A Review of Ruxolitinib for the Treatment of Myelofibrosis: A Critique of the Evidence

Methodological challenges in the development of endpoints for myelofibrosis clinical trials

Myelofibrosis is a myeloid neoplasm characterised by the presence of JAK2, CALR, or MPL mutations (with a 90% mutation frequency) and trilineage myeloid proliferation with prominent megakaryocyte atypia. People with myelofibrosis have a lower survival rate and poorer quality of life than healthy individuals. Therapy for myelofibrosis uses Janus kinase inhibitors, which reduce splenomegaly and alleviate symptoms. Regulatory approvals for Janus kinase inhibitors have focused on this dual endpoint. In this Viewpoint, we discuss the validity of using spleen reduction as a surrogate endpoint for the disease-modifying activity of candidate drugs for myelofibrosis. We suggest alternative endpoints addressing unmet patient needs, including progression-free survival and overall survival. Moreover, we highlight the importance of selecting a core set of crucial outcomes with which we can individualise clinical decision making and standardise reporting of clinical trials results. We propose selecting patient-reported outcomes and anaemia response. We also suggest integrating economic considerations in the process of evaluating new drugs for myelofibrosis.

Anticancer properties of chimeric HDAC and kinase inhibitors

Histone deacetylases (HDACs) are epigenetic regulators of chromatin condensation and decondensation and exert effects on the proliferation and spread of cancer. Thus, HDAC enzymes are promising drug targets for the treatment of cancer. Some HDAC inhibitors such as the hydroxamic acid derivatives vorinostat or panobinostat were already approved for the treatment of hematologic cancer diseases, and are under intensive investigation for their use in solid tumors. But there are also drawbacks of the clinical application of HDAC inhibitors like intrinsic or acquired drug resistance and, thus, new HDAC inhibitors with improved activities are sought for. Kinase inhibitors are very promising anticancer drugs and often showed synergistic anticancer effects in combination with HDAC inhibitors. Several hybrid molecules with HDAC and kinase inhibitory structural motifs were disclosed with even improved anticancer activities when compared with co-application of HDAC and receptor tyrosine kinase inhibitors. Chimeric inhibitors with HDAC inhibitory activities exert a rapidly growing field of research and only in this year several new dual HDAC/kinase inhibitors were disclosed. This review briefly summarizes the status and future perspective of the most advanced and promising dual HDAC/kinase inhibitors and their potential as anticancer drug candidates.

Efficacy of JAK inhibitors in Crohn's Disease

Inhibition of Janus kinases [JAKs] in Crohn's disease [CD] patients has shown conflicting results in clinical trials. Tofacitinib, a pan-JAK inhibitor, showed efficacy in ulcerative colitis [UC] and has been approved for the treatment of patients with moderate to severe UC. In contrast, studies in CD patients were disappointing and the primary end point of clinical remission could not be met in the respective phase II induction and maintenance trials. Subsequently, the clinical development of tofacitinib was discontinued in CD. In contrast, efficacy of filgotinib, a selective JAK1 inhibitor, in CD patients was demonstrated in the randomized, double-blinded, placebo-controlled phase II FITZROY study. Upadacitinib also showed promising results in a phase II trial in moderate to severe CD. Subsequently, phase III programmes in CD have been initiated for both substances, which are still ongoing. Several newer molecules of this class of orally administrated immunosuppressants are being tested in clinical programmes. The concern of side effects of systemic JAK inhibition is addressed by either exclusively intestinal action or higher selectivity [Tyk2 inhibitors]. In general, JAK inhibitors constitute a new promising class of drugs for the treatment of CD.

Ruxolitinib Alleviates Renal Interstitial Fibrosis in UUO Mice

Ruxolitinib is a selective inhibitor of Jak1/2. Downstream signaling pathways of Jak, such as Stat3 and Akt/mTOR, are overactivated and contribute to renal interstitial fibrosis. Therefore, we explored the effect of Ruxolitinib on this pathological process. Unilateral ureteral obstruction (UUO) models and TGF-β1-treated fibroblasts and renal tubular epithelial cells were adopted in this study. Ruxolitinib was administered to UUO mice and TGF-β1-treated cells. Kidneys from UUO mice with Ruxolitinib treatment displayed less tubular injuries compared with those without Ruxolitinib treatment. Ruxolitinib treatment suppressed fibroblast activation and extracellular matrix (ECM) production in UUO kidneys and TGF-β1-treated fibroblasts. Ruxolitinib treatment also blocked epithelial-mesenchymal transition (EMT) in UUO kidneys and TGF-β 1-treated renal tubular epithelial cells. Moreover, Ruxolitinib treatment alleviated UUO-induced inflammation, oxidative stress and apoptosis. Mechanistically, Ruxolitinib treatment attenuated activation of both Stat3 and Akt/mTOR/Yap pathways. In conclusion, Ruxolitinib treatment can ameliorate UUO-induced renal interstitial fibrosis, suggesting that Ruxolitinib may be potentially used to treat fibrotic kidney disease.

Ruxolitinib combined with vorinostat suppresses tumor growth and alters metabolic phenotype in hematological diseases

JAK-2 dysregulation plays an important role as an oncogenic driver, and is thus a promising therapeutic target in hematological malignancies. Ruxolitinib is a pyrrolo[2.3-d]pyrimidine derivative with inhibitory activity against JAK1 and JAK2, moderate activity against TYK2, and minor activity against JAK3. Vorinostat is an HDAC inhibitor that reduces JAK-2 expression, thus affecting JAK-2 mRNA expression and increasing JAK-2 proteasomal deterioration. Here we hypothesized that the combination of ruxolitinib and vorinostat could have synergistic effects against hematological disease. We tested combinations of low doses of ruxolitinib and vorinostat in 12 cell lines, and observed highly synergistic cytotoxic action in six cell lines, which was maintained for up to 120 h in the presence of stromal cells. The sensitivity of the six cell lines may be explained by the broad effects of the drug combination, which can affect various targets. Treatment with the combination of ruxolitinib and vorinostat appeared to induce a possible reversal of the Warburg effect, with associated ROS production, apoptotic events, and growth inhibition. Decreased glucose metabolism may have markedly sensitized the six more susceptible cell lines to combined treatment. Therapeutic inhibition of the JAK/STAT pathway seems to offer substantial anti-tumor benefit, and combined therapy with ruxolitinib and vorinostat may represent a promising novel therapeutic modality for hematological neoplasms.

Cost-effectiveness of kinase inhibitors for hematologic malignancies: a systematic and critical review

INTRODUCTION

Several genetic disruptions lead to constitutive activation of those kinases leukemic cells depend on for survival and proliferation. Kinase inhibitors (KI) are major therapeutic innovations for chronic myeloid leukemia (CML), chronic lymphoid leukemia (CLL) and myelofibrosis (MF) providing a relevant improvement of quality-adjusted survival in patients with high-risk or refractory disease. CML patients are being treated with first-generation KI imatinib since many years, achieving expected survivals longer than 10 years. Second- and third generations KIs, such as nilotinib, dasatinib, ponatinib and bosutinib, recently expanded the therapeutic yield for CML and treatment discontinuation in patients with persistent deep molecular response is being pursued. Areas covered: This review summarizes available evidence on economic analyses of KI treatments for CML, CLL and MF aimed at identifying the key determinants of KI cost-effectiveness. Expert commentary: On converse, specific KIs for CLL and MF patients have been marketed only in the last few years. Ibrutinib and idelalisib allowed to improve the outcomes of relapsed/refractory CLL and of patients with poor genetic features, while the first-in-class JAK2 inhibitor ruxolitinib allowed to improve symptoms of advanced MF patients and to prolong survival in responders. In the current situation of healthcare budget restrictions worldwide, the value for cost of the above KIs has been questioned.