Revisiting Structure-activity Relationships: Unleashing the potential of selective Janus kinase 1 inhibitors.

Janus kinases (JAKs), a kind of non-receptor tyrosine kinases, the function has been implicated in the regulation of cell proliferation, differentiation and apoptosis, immune, inflammatory response and malignancies. Among them, JAK1 represents an essential target for modulating cytokines involved in inflammation and immune function. Rheumatoid arthritis, atopic dermatitis, ulcerative colitis and psoriatic arthritis are areas where approved JAK1 drugs have been applied for the treatment. In the review, we provided a brief introduction to JAK1 inhibitors in market and clinical trials. The structures of high active JAK1 compounds (IC50 ≤ 0.1 nM) were highlighted, with primary focus on structure-activity relationship and selectivity. Moreover, the druggability processes of approved drugs and high active compounds were analyzed. In addition, the issues involved in JAK1 compounds clinical application as well as strategies to surmount these challenges, were discussed.

Evaluation of ruxolitinib cream 1.5% as an at-home therapy for repigmentation in non-segmental vitiligo.

INTRODUCTION: Vitiligo is a chronic, autoimmune condition characterized by skin depigmentation caused by inflammatory-mediated melanocyte degradation. Treatment of vitiligo is challenging due to the chronic nature of the condition. Ruxolitinib cream 1.5% was recently approved by the Food and Drug Administration (FDA) as a Janus kinase 1 and 2 inhibitor for use in nonsegmental vitiligo for those 12 years and older. AREAS COVERED: The purpose of this review is to describe the role of ruxolitinib in treating nonsegmental vitiligo.We searched PubMed using search terms nonsegmental vitiligo, jak inhibitor, and ruxolitinib. Clinicaltrials.gov was used to identify clinical trial data including efficacy, pharmacodynamics, pharmacokinetics, safety, and tolerability. EXPERT OPINION: In both phase II and phase III (TRuE-V1 and TRuE-V2) trials, ruxolitinib cream 1.5% improved repigmentation with minimal adverse effects. Topical ruxolitinib is a much needed new vitiligo treatment option.  Real life efficacy may not match that seen in clinical trials if the hurdle of poor adherence to topical treatment is not surmounted.

Peripheral cytokine interleukin-10 alleviates perihematomal edema after intracerebral hemorrhage via interleukin-10 receptor/JAK1/STAT3 signaling.

AIMS: The extent of perihematomal edema following intracerebral hemorrhage (ICH) significantly impacts patient prognosis, and disruption of the blood-brain barrier (BBB) exacerbates perihematomal edema. However, the role of peripheral IL-10 in mitigating BBB disruption through pathways that link peripheral and central nervous system signals remains poorly understood. METHODS: Recombinant IL-10 was administered to ICH model mice via caudal vein injection, an IL-10-inhibiting adeno-associated virus and an IL-10 receptor knockout plasmid were delivered intraventricularly, and neurobehavioral deficits, perihematomal edema, BBB disruption, and the expression of JAK1 and STAT3 were evaluated. RESULTS: Our study demonstrated that the peripheral cytokine IL-10 mitigated BBB breakdown, perihematomal edema, and neurobehavioral deficits after ICH and that IL-10 deficiency reversed these effects, likely through the IL-10R/JAK1/STAT3 signaling pathway. CONCLUSIONS: Peripheral IL-10 has the potential to reduce BBB damage and perihematomal edema following ICH and improve patient prognosis.

Discovery of a potent and selective JAK1-targeting PROTAC degrader with anti-tumor activities.

Aberrant activation of the JAK-STAT pathway is evident in various human diseases including cancers. Proteolysis targeting chimeras (PROTACs) provide an attractive strategy for developing novel JAK-targeting drugs. Herein, a series of CRBN-directed JAK-targeting PROTACs were designed and synthesized utilizing a JAK1/JAK2 dual inhibitor-momelotinib as the warhead. The most promising compound 10c exhibited both good enzymatic potency and cellular antiproliferative effects. Western blot analysis revealed that compound 10c effectively and selectively degraded JAK1 in a proteasome-dependent manner (DC50 = 214 nM). Moreover, PROTAC 10c significantly suppressed JAK1 and its key downstream signaling. Together, compound 10c may serve as a novel lead compound for antitumor drug discovery.

Combined JAK inhibition and PD-1 immunotherapy for non-small cell lung cancer patients.

Persistent inflammation driven by cytokines such as type-one interferon (IFN-I) can cause immunosuppression. We show that administration of the Janus kinase 1 (JAK1) inhibitor itacitinib after anti-PD-1 (programmed cell death protein 1) immunotherapy improves immune function and antitumor responses in mice and results in high response rates (67%) in a phase 2 clinical trial for metastatic non-small cell lung cancer. Patients who failed to respond to initial anti-PD-1 immunotherapy but responded after addition of itacitinib had multiple features of poor immune function to anti-PD-1 alone that improved after JAK inhibition. Itacitinib promoted CD8 T cell plasticity and therapeutic responses of exhausted and effector memory-like T cell clonotypes. Patients with persistent inflammation refractory to itacitinib showed progressive CD8 T cell terminal differentiation and progressive disease. Thus, JAK inhibition may improve the efficacy of anti-PD-1 immunotherapy by pivoting T cell differentiation dynamics.

Co-targeting JAK1/STAT6/GAS6/TAM signaling improves chemotherapy efficacy in Ewing sarcoma.

Ewing sarcoma is a pediatric bone and soft tissue tumor treated with chemotherapy, radiation, and surgery. Despite intensive multimodality therapy, ~50% patients eventually relapse and die of the disease due to chemoresistance. Here, using phospho-profiling, we find Ewing sarcoma cells treated with chemotherapeutic agents activate TAM (TYRO3, AXL, MERTK) kinases to augment Akt and ERK signaling facilitating chemoresistance. Mechanistically, chemotherapy-induced JAK1-SQ phosphorylation releases JAK1 pseudokinase domain inhibition allowing for JAK1 activation. This alternative JAK1 activation mechanism leads to STAT6 nuclear translocation triggering transcription and secretion of the TAM kinase ligand GAS6 with autocrine/paracrine consequences. Importantly, pharmacological inhibition of either JAK1 by filgotinib or TAM kinases by UNC2025 sensitizes Ewing sarcoma to chemotherapy in vitro and in vivo. Excitingly, the TAM kinase inhibitor MRX-2843 currently in human clinical trials to treat AML and advanced solid tumors, enhances chemotherapy efficacy to further suppress Ewing sarcoma tumor growth in vivo. Our findings reveal an Ewing sarcoma chemoresistance mechanism with an immediate translational value.

Synthesis, Antiproliferative Activity and Molecular Docking Analysis of Both Enantiomerically Pure Decursin Derivatives as Anticancer Agents.

Using (S)-decursinol isolated from root of Angelica gigas Nakai (AGN), we semi-synthesized and evaluated a series of both enantiomerically pure decursin derivatives for their antiproliferative activities against A549 human lung cancer cells. All synthesized compounds showed a broad spectrum of inhibitory activities against the growth of A549 cells. Especially, compound (S)-2d with (E)-(furan-3-yl)acryloyl group showed the most potent activity (IC50: 14.03 µM) against A549 cancer cells as compared with the reference compound, decursin (IC50: 43.55 µM) and its enantiomer, (R)-2d (IC50: 151.59 µM). Western blotting assays indicated that (S)-2d more strongly inhibited Janus kinase 1 (JAK1) and signal transducer and activator of transcription activation 3 (STAT3) phosphorylation than decursin in a dose-dependent manner, while having no effect on CXCR7 overexpression and total STAT3 level. In addition, (S)-2d induced cell cycle arrest at G1 phase and subsequent apoptotic cell death in A549 cancer cells. Our combined analysis of molecular docking studies and biological data suggests that the inhibition of JAK1 with (S)-2d resulted in loss of STAT3 phosphorylation and inhibition of cell growth in A549 cancer cells. These overall results strongly suggest that (S)-2d (MRC-D-004) as a novel JAK1 inhibitor may have therapeutic potential in the treatment of A549 human lung cancers by targeting the JAK1/STAT3 signaling pathway.

A Novel JAK1 Inhibitor SHR0302 Combined With Prednisone for First-Line Treatment of Chronic Graft-Versus-Host Disease: A Phase I Clinical Trial.

Chronic graft-versus-host disease (cGVHD) is a potentially life-threatening complication after allogeneic hematopoietic stem cell transplantation. Standard steroid first-line treatment could not satisfy therapeutic needs due to limited efficacy. As a highly selective Janus kinase (JAK) 1 inhibitor, SHR0302 exhibits a reduced inhibition effect on JAK2 and might have less effect on hematopoiesis. This phase I clinical trial investigated the tolerability and safety of SHR0302 in combination with prednisone, and its early efficacy evidence as a potential first-line treatment to moderate/severe cGVHD. The standard 3 + 3 dose escalation was implemented to find the optimal dose of SHR0302. And prednisone was concurrently administrated with a dose of 1 mg/kg/d and then gradually tapered after 2 weeks. Eighteen patients were enrolled into the study. Grade ≥ 3 treatment-related adverse events were observed in 38.9% of patients. Only one patient developed DLT (grade ≥ 3 hypercholesterolemia) in the highest dose-level group who had pre-existing hypercholesterolemia. The maximum tolerated dose was not reached. No patient discontinued treatment due to AEs. Sixteen out of 18 patients were evaluable for responses, the ORR at week 4 and week 24 were 94.4 and 87.5%, respectively. Overall, the treatment of SHR0302 combined with prednisone was safe and well-tolerated, preliminary clinical results presented a high response for previously untreated cGVHD and a significant reduction in prednisone use in this study. A phase II trial will be conducted to further investigate its therapeutic effects clinically.

Evaluating the pharmacokinetics of upadacitinib for the treatment of moderate-to-severe Crohn's disease.

INTRODUCTION: Janus kinases (JAK) are enzymes involved in signaling pathways that activate the immune system. Upadacitinib, an oral small molecule, is the first JAK inhibitor approved by FDA and EMA for the treatment of moderately to severely active Crohn's disease (CD), following successful phase II and III trials. Compared to other JAK inhibitors, upadacitinib has a high selectivity toward JAK1. This characteristic could improve its efficacy and safety. AREAS COVERED: This review provides an overview of the available knowledge on the pharmacokinetics of upadacitinib as induction and maintenance therapy for CD. EXPERT OPINION: The approval of newer targeted small molecules drug, including JAK inhibitors, marked a significant advancement in terms of effectiveness. In fact, the oral administration, the rapid absorption, the excellent bioavailability and the short serum time of maximum concentration are some of the advantages compared to biologics. The selective inhibition of JAK1 by upadacitinib allows for high efficacy while maintaining a reliable safety profile.

Subcutaneous administration of Stattic alleviates neuropathic pain by relieving inflammation in a mouse model of postherpetic neuralgia.

Stattic, a commercial inhibitor of STAT3, can drive the development of neuropathic pain. Exploring the connection between Stattic and JAK1/STAT3 signaling may facilitate the understanding of neuropathic pain caused by postherpetic neuralgia (PHN). In the current study, as crucial regulators of inflammation, STAT3 and its associated JAK1/STAT3 pathway were found to be upregulated and activated in the L4-L6 dorsal root ganglion (DRG) of mice in response to resiniferatoxin (RTX)-induced PHN, while subcutaneous administration of Stattic was found to downregulate STAT3 expression and phosphorylation in a PHN model. Stattic administration further attenuated hypersensitivity to mechanical and thermal stimuli in PHN mice, and alleviated inflammation and cell death in the L4-L6 DRG of mice. Overexpression of STAT3 via microinjection of a lentiviral-STAT3 overexpression vector reversed the abnormal decrease of STAT3 at both the mRNA and protein levels in the L4-6 DRGs of PHN mice and significantly promoted hypersensitivity to mechanical stimuli in the mice. Collectively, we found that subcutaneous static administration alleviated RTX-induced neuropathic pain by deactivating JAK1/STAT3 in mice.

Efficacy, Safety, and Long-Term Disease Control of Ruxolitinib Cream Among Adolescents with Atopic Dermatitis: Pooled Results from Two Randomized Phase 3 Studies.

BACKGROUND: Atopic dermatitis (AD), a highly pruritic, inflammatory skin disease, affects approximately 7% of adolescents globally. A topical formulation of ruxolitinib, a Janus kinase (JAK) 1/JAK2 inhibitor, demonstrated safety and efficacy among adolescents/adults in two phase 3 studies (TRuE-AD1/TRuE-AD2). OBJECTIVE: To describe safety and efficacy of 1.5% ruxolitinib cream versus vehicle and long-term disease control of ruxolitinib cream among adolescents aged 12-17 years from pooled phase 3 study data. METHODS: Patients [≥ 12 years old with AD for ≥ 2 years, Investigator's Global Assessment score (IGA) 2/3, and 3-20% affected body surface area (BSA) at baseline] were randomized 2:2:1 to ruxolitinib cream (0.75%/1.5%) or vehicle for 8 weeks of continuous use followed by a long-term safety (LTS) period up to 52 weeks with as-needed use. Patients originally applying vehicle were rerandomized 1:1 to 0.75%/1.5% ruxolitinib cream. Efficacy measures at week 8 included IGA treatment success (IGA-TS; i.e., score of 0/1 with ≥ 2 grade improvement from baseline), ≥ 75% improvement in Eczema Area and Severity Index (EASI-75), and ≥ 4-point improvement in itch numerical rating scale (NRS4). Measures of disease control during the LTS period included IGA score of 0 (clear) or 1 (almost clear) and percentage affected BSA. Safety was assessed throughout the study. RESULTS: Of 1249 randomized patients, 245 (19.6%) were aged 12-17 years. Of these, 45 patients were randomized to vehicle and 92 patients to 1.5% ruxolitinib cream. A total of 104/137 (75.9%) patients continued on 1.5% ruxolitinib cream in the LTS period [82/92 (89.1%) continued on 1.5% ruxolitinib cream; 22/45 (48.9%) patients on vehicle were reassigned to 1.5% ruxolitinib cream], and 83/104 (79.8%) of these patients completed the LTS period. At week 8, substantially more patients who applied 1.5% ruxolitinib cream versus vehicle achieved IGA-TS (50.6% versus 14.0%), EASI-75 (60.9% versus 34.9%), and NRS4 (52.1% versus 17.4%; P = 0.009). The mean (SD) reduction in itch NRS scores was significantly greater in patients applying 1.5% ruxolitinib cream versus vehicle from day 2 [- 0.9 (1.9) versus -0.2 (1.4); P = 0.03]. During the LTS period, mean (SD) trough steady-state ruxolitinib plasma concentrations at weeks 12/52 were 27.2 (55.7)/15.5 (31.5) nM. The percentage of patients achieving IGA score of 0 or 1 was sustained or further increased with 1.5% ruxolitinib cream; mean affected BSA was generally low (< 3%; i.e., mild disease). Through 52 weeks, application site reactions occurred in 1.8% of adolescent patients applying 1.5% ruxolitinib cream at any time; no patients had serious adverse events. There were no serious infections, malignancies, major adverse cardiovascular events, or thromboembolic events. CONCLUSIONS: Meaningful anti-inflammatory and antipruritic effects were demonstrated with 1.5% ruxolitinib cream in the subset of adolescent patients with AD, comparable with those observed in the overall study population; long-term, as-needed use maintained disease control and was well tolerated. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov identifiers NCT03745638 (registered 19 November 2018) and NCT03745651 (registered 19 November 2018).

Reversible effects on female rat fertility with abrocitinib, a Janus kinase 1 inhibitor.

BACKGROUND: Abrocitinib is a Janus kinase (JAK) 1 selective inhibitor approved for the treatment of atopic dermatitis. Female reproductive tissues were unaffected in general toxicity studies, but an initial female rat fertility study resulted in adverse effects at all doses evaluated. A second rat fertility study was conducted to evaluate lower doses and potential for recovery. METHODS: This second study had 4 groups of 20 females each administered abrocitinib (0, 3, 10, or 70 mg/kg/day) 2 weeks prior to cohabitation through gestation day (GD) 7. In addition, 2 groups of 20 rats (0 or 70 mg/kg/day) were dosed for 3 weeks followed by a 4-week recovery period before mating. All mated females were evaluated on GD 14. RESULTS: No effects were observed at ≤10 mg/kg/day. At 70 mg/kg/day (29x human exposure), decreased pregnancy rate, implantation sites, and viable embryos were observed. All these effects reversed 4 weeks after the last dose. CONCLUSIONS: Based on these data and literature on the potential role of JAK signaling in implantation, we hypothesize that these effects may be related to JAK1 inhibition and, generally, that peri-implantation effects such as these, in the absence of cycling or microscopic changes in nonpregnant female reproductive tissues, are anticipated to be reversible.

Enhancement of vincristine sensitivity in retinoblastoma through Janus kinase inhibition by ruxolitinib.

Chemotherapy remains the main approach conserving vision during the treatment of retinoblastoma, the most prevalent eye cancer in children. Unfortunately, the development of chemoresistance stands as the primary reason for treatment failure. Within this study, we showed that prolonged exposure to vincristine led to heightened expression of JAK1 and JAK2 in retinoblastoma cells, while the other members of the JAK family exhibited no such changes. Employing a genetic intervention, we demonstrated the efficacy of depleting either JAK1 or JAK2 in countering vincristine-resistant retinoblastoma cells. In addition, the dual depletion of both JAK1 and JAK2 produced a more potent inhibitory outcome compared to the depletion of either gene alone. We further demonstrated that ruxolitinib, a small molecular inhibitor of JAK1/2, effectively reduced viability and colony formation in vincristine-resistant retinoblastoma cells. It also acts synergistically with vincristine in retinoblastoma cells regardless of inherent cellular and genetic heterogeneity. The effectiveness of ruxolitinib as standalone treatment against chemoresistant retinoblastoma, as well as its combination with vincristine, was validated in multiple retinoblastoma mouse models. Importantly, mice exhibited favorable tolerance to ruxolitinib administration. We confirmed that the underlying mechanism of ruxolitinib's action in chemoresistant retinoblastoma cells is the inhibition of Janus kinase/signal transducer and activator of transcription (JAK/STAT) signaling. Our study reveals that the underlying mechanism driving ruxolitinib's impact on chemoresistant retinoblastoma cells is the inhibition of JAK/STAT signaling. This study reveals the contribution of JAK1/2 to the development of chemoresistance in retinoblastoma and underscores the effectiveness of targeting JAK1/2 as a strategy to sensitize retinoblastoma to chemotherapy.

The Metabolism and Disposition of Brepocitinib in Humans and Characterization of the Formation Mechanism of an Aminopyridine Metabolite.

Brepocitinib is an oral once-daily Janus kinase 1 and Tyrosine kinase 2 selective inhibitor currently in development for the treatment of several autoimmune disorders. Mass balance and metabolic profiles were determined using accelerator mass spectrometry in six healthy male participants following a single oral 60 mg dose of 14C-brepocitinib (∼300 nCi). The average mass balance recovery was 96.7% ± 6.3%, with the majority of dose (88.0% ± 8.0%) recovered in urine and 8.7% ± 2.1% of the dose recovered in feces. Absorption of brepocitinib was rapid, with maximal plasma concentrations of total radioactivity and brepocitinib achieved within 0.5 hours after dosing. Circulating radioactivity consisted primarily of brepocitinib (47.8%) and metabolite M1 (37.1%) derived from hydroxylation at the C5' position of the pyrazole ring. Fractional contributions to metabolism via cytochrome P450 enzymes were determined to be 0.77 for CYP3A4/5 and 0.14 for CYP1A2 based on phenotyping studies in human liver microsomes. However, additional clinical studies are required to understand the potential contribution of CYP1A1. Approximately 83% of the dose was eliminated as N-methylpyrazolyl oxidative metabolites, with 52.1% of the dose excreted as M1 alone. Notably, M1 was not observed as a circulating metabolite in earlier metabolic profiling of human plasma from a multiple ascending dose study with unlabeled brepocitinib. Mechanistic studies revealed that M1 was highly unstable in human plasma and phosphate buffer, undergoing chemical oxidation leading to loss of the 5-hydroxy-1-methylpyrazole moiety and formation of aminopyrimidine cleavage product M2. Time-dependent inhibition and trapping studies with M1 yielded insights into the mechanism of this unusual and unexpected instability. SIGNIFICANCE STATEMENT: This study provides a detailed understanding of the disposition and metabolism of brepocitinib, a JAK1/TYK2 inhibitor for atopic dermatitis, in humans as well as characterization of clearance pathways and pharmacokinetics of brepocitinib and its metabolites.

Tofacitinib and peficitinib inhibitors of Janus kinase for autoimmune disease treatment: a quantum biochemistry approach.

Autoimmune inflammatory diseases, such as rheumatoid arthritis (RA) and ulcerative colitis, are associated with an uncontrolled production of cytokines leading to the pronounced inflammatory response of these disorders. Their therapy is currently focused on the inhibition of cytokine receptors, such as the Janus kinase (JAK) protein family. Tofacitinib and peficitinib are JAK inhibitors that have been recently approved to treat rheumatoid arthritis. In this study, an in-depth analysis was carried out through quantum biochemistry to understand the interactions involved in the complexes formed by JAK1 and tofacitinib or peficitinib. Computational analyses provided new insights into the binding mechanisms between tofacitinib or peficitinib and JAK1. The essential amino acid residues that support the complex are also identified and reported. Additionally, we report new interactions, such as van der Waals; hydrogen bonds; and alkyl, pi-alkyl, and pi-sulfur forces, that stabilize the complexes. The computational results revealed that peficitinib presents a similar affinity to JAK1 compared to tofacitinib based on their interaction energies.

Novel JAK Inhibitors to Reduce Graft-Versus-Host Disease after Allogeneic Hematopoietic Cell Transplantation in a Preclinical Mouse Model.

Allogeneic hematopoietic cell transplantation (allo-HCT) is a highly effective, well-established treatment for patients with various hematologic malignancies and non-malignant diseases. The therapeutic benefits of allo-HCT are mediated by alloreactive T cells in donor grafts. However, there is a significant risk of graft-versus-host disease (GvHD), in which the donor T cells recognize recipient cells as foreign and attack healthy organs in addition to malignancies. We previously demonstrated that targeting JAK1/JAK2, mediators of interferon-gamma receptor (IFNGR) and IL-6 receptor signaling, in donor T cells using baricitinib and ruxolitinib results in a significant reduction in GvHD after allo-HCT. Furthermore, we showed that balanced inhibition of JAK1/JAK2 while sparing JAK3 is important for the optimal prevention of GvHD. Thus, we have generated novel JAK1/JAK2 inhibitors, termed WU derivatives, by modifying baricitinib. Our results show that WU derivatives have the potential to mitigate GvHD by upregulating regulatory T cells and immune reconstitution while reducing the frequencies of antigen-presenting cells (APCs) and CD80 expression on these APCs in our preclinical mouse model of allo-HCT. In addition, WU derivatives effectively downregulated CXCR3 and T-bet in primary murine T cells. In summary, we have generated novel JAK inhibitors that could serve as alternatives to baricitinib or ruxolitinib.

Employing zero-inflated beta distribution in an exposure-response analysis of TYK2/JAK1 inhibitor brepocitinib in patients with plaque psoriasis.

Brepocitinib is an oral selective dual TYK2/JAK1 inhibitor and based on its cytokine inhibition profile is expected to provide therapeutic benefit in the treatment of plaque psoriasis. Efficacy data from a completed Phase 2a study in patients with moderate-to-severe plaque psoriasis were utilized to develop a population exposure-response model that can be employed to inform dose selection decisions for further clinical development. A modeling approach that employs the zero-inflated beta distribution was used to account for the bounded nature and distributional characteristics of the Psoriasis Area and Severity Index (PASI) score data. The developed exposure-response model provided an adequate description of the observed PASI scores across all the treatment arms tested and across both the induction and maintenance dosing periods of the study. In addition, the developed model exhibited a good predictive capacity with regard to the derived responder metrics (e.g., 75%/90%/100% improvement in PASI score [PASI75/90/100]). Clinical trial simulations indicated that the induction/maintenance dosing paradigm explored in this study does not offer any advantages from an efficacy perspective and that doses of 10, 30, and 60 mg once-daily may be suitable candidates for clinical evaluation in subsequent Phase 2b studies.

Differential effects of itacitinib, fedratinib, and ruxolitinib in mouse models of hemophagocytic lymphohistiocytosis.

ABSTRACT: Hemophagocytic lymphohistiocytosis (HLH) comprises a severe hyperinflammatory phenotype driven by the overproduction of cytokines, many of which signal via the JAK/STAT pathway. Indeed, the JAK1/2 inhibitor ruxolitinib has demonstrated efficacy in preclinical studies and early-phase clinical trials in HLH. Nevertheless, concerns remain for ruxolitinib-induced cytopenias, which are postulated to result from the blockade of JAK2-dependent hematopoietic growth factors. To explore the therapeutic effects of selective JAK inhibition in mouse models of HLH, we carried out studies incorporating the JAK1 inhibitor itacitinib, JAK2 inhibitor fedratinib, and JAK1/2 inhibitor ruxolitinib. All 3 drugs were well-tolerated and at the doses tested, they suppressed interferon-gamma (IFN-γ)-induced STAT1 phosphorylation in vitro and in vivo. Itacitinib, but not fedratinib, significantly improved survival and clinical scores in CpG-induced secondary HLH. Conversely, in primary HLH, in which perforin-deficient (Prf1-/-) mice are infected with lymphocytic choriomeningitis virus (LCMV), itacitinib, and fedratinib performed suboptimally. Ruxolitinib demonstrated excellent clinical efficacy in both HLH models. RNA-sequencing of splenocytes from LCMV-infected Prf1-/- mice revealed that itacitinib targeted inflammatory and metabolic pathway genes in CD8 T cells, whereas fedratinib targeted genes regulating cell proliferation and metabolism. In monocytes, neither drug conferred major transcriptional impacts. Consistent with its superior clinical effects, ruxolitinib exerted the greatest transcriptional changes in CD8 T cells and monocytes, targeting more genes across several biologic pathways, most notably JAK-dependent proinflammatory signaling. We conclude that JAK1 inhibition is sufficient to curtail CpG-induced disease, but combined inhibition of JAK1 and JAK2 is needed to best control LCMV-induced immunopathology.

Momelotinib vs. ruxolitinib in myelofibrosis patient subgroups by baseline hemoglobin levels in the SIMPLIFY-1 trial.

A key hallmark of myelofibrosis is anemia, which ranges from mild to severe based on hemoglobin levels. To more clearly define outcomes with the Janus kinase (JAK) 1/JAK2/activin A receptor type 1 inhibitor momelotinib by anemia severity, we performed a descriptive post hoc exploratory analysis of the double-blind, randomized, phase 3 SIMPLIFY-1 study (NCT01969838; N = 432, JAK inhibitor naive, momelotinib vs. ruxolitinib); subgroups were defined by baseline hemoglobin: <10 (moderate/severe), ≥10 to <12 (mild), or ≥12 g/dL (nonanemic). Spleen and symptom results were generally consistent with those previously reported for the intent-to-treat population. In anemic subgroups, momelotinib was associated with higher rates of transfusion independence and reduced/stable transfusion intensity vs. ruxolitinib. No new or unexpected safety signals were identified. Overall, momelotinib provides spleen, symptom, and anemia benefits to JAK inhibitor-naive patients with myelofibrosis regardless of baseline hemoglobin level, and greater anemia-related benefits vs. ruxolitinib in patients with hemoglobin <12 g/dL.