Parsaclisib Is a Next-Generation Phosphoinositide 3-Kinase δ Inhibitor with Reduced Hepatotoxicity and Potent Antitumor and Immunomodulatory Activities in Models of B-Cell Malignancy.

The clinical use of first-generation phosphoinositide 3-kinase (PI3K)δ inhibitors in B-cell malignancies is hampered by hepatotoxicity, requiring dose reduction, treatment interruption, and/or discontinuation of therapy. In addition, potential molecular mechanisms by which resistance to this class of drugs occurs have not been investigated. Parsaclisib (INCB050465) is a potent and selective next-generation PI3Kδ inhibitor that differs in structure from first-generation PI3Kδ inhibitors and has shown encouraging anti-B-cell tumor activity and reduced hepatotoxicity in phase 1/2 clinical studies. Here, we present preclinical data demonstrating parsaclisib as a potent inhibitor of PI3Kδ with over 1000-fold selectivity against other class 1 PI3K isozymes. Parsaclisib directly blocks PI3K signaling-mediated cell proliferation in B-cell lines in vitro and in vivo and indirectly controls tumor growth by lessening immunosuppression through regulatory T-cell inhibition in a syngeneic lymphoma model. Diffuse large B-cell lymphoma cell lines overexpressing MYC were insensitive to proliferation blockade via PI3Kδ signaling inhibition by parsaclisib, but their proliferative activities were reduced by suppression of MYC gene transcription. Molecular structure analysis of the first- and next-generation PI3Kδ inhibitors combined with clinical observation suggests that hepatotoxicity seen with the first-generation inhibitors could result from a structure-related off-target effect. Parsaclisib is currently being evaluated in multiple phase 2 clinical trials as a therapy against various hematologic malignancies of B-cell origin (NCT03126019, NCT02998476, NCT03235544, NCT03144674, and NCT02018861). SIGNIFICANCE STATEMENT: The preclinical properties described here provide the mechanism of action and support clinical investigations of parsaclisib as a therapy for B-cell malignancies. MYC overexpression was identified as a resistance mechanism to parsaclisib in DLBCL cells, which may be useful in guiding further translational studies for the selection of patients with DLBCL who might benefit from PI3Kδ inhibitor treatment in future trials. Hepatotoxicity associated with first-generation PI3Kδ inhibitors may be an off-target effect of that class of compounds.

INCB040093 Is a Novel PI3Kδ Inhibitor for the Treatment of B Cell Lymphoid Malignancies.

Phosphatidylinositol 3-kinase delta (PI3Kδ) is a critical signaling molecule in B cells and is considered a target for development of therapies against various B cell malignancies. INCB040093 is a novel PI3Kδ small-molecule inhibitor and has demonstrated promising efficacy in patients with Hodgkin's lymphoma in clinical studies. In this study, we disclose the chemical structure and the preclinical activity of the compound. In biochemical assays, INCB040093 potently inhibits the PI3Kδ kinase, with 74- to >900-fold selectivity against other PI3K family members. In vitro and ex vivo studies using primary B cells, cell lines from B cell malignancies, and human whole blood show that INCB040093 inhibits PI3Kδ-mediated functions, including cell signaling and proliferation. INCB040093 has no significant effect on the growth of nonlymphoid cell lines and was less potent in assays that measure human T and natural killer cell proliferation and neutrophil and monocyte functions, suggesting that the impact of INCB040093 on the human immune system will likely be restricted to B cells. INCB040093 inhibits the production of macrophage-inflammatory protein-1ß (MIP-1beta) and tumor necrosis factor-ß (TNF-beta) from a B cell line, suggesting a potential effect on the tumor microenvironment. In vivo, INCB040093 demonstrates single-agent activity in inhibiting tumor growth and potentiates the antitumor growth effect of the clinically relevant chemotherapeutic agent, bendamustine, in the Pfeiffer cell xenograft model of non-Hodgkin's lymphoma. INCB040093 has a favorable exposure profile in rats and an acceptable safety margin in rats and dogs. Taken together, data presented in this report support the potential utility of orally administered INCB040093 in the treatment of B cell malignancies.

Characterization of INCB086550: A Potent and Novel Small-Molecule PD-L1 Inhibitor.

Blocking the activity of the programmed cell death protein 1 (PD-1) inhibitory receptor with therapeutic antibodies against either the ligand (PD-L1) or PD-1 itself has proven to be an effective treatment modality for multiple cancers. Contrasting with antibodies, small molecules could demonstrate increased tissue penetration, distinct pharmacology, and potentially enhanced antitumor activity. Here, we describe the identification and characterization of INCB086550, a novel, oral, small-molecule PD-L1 inhibitor. In vitro, INCB086550 selectively and potently blocked the PD-L1/PD-1 interaction, induced PD-L1 dimerization and internalization, and induced stimulation-dependent cytokine production in primary human immune cells. In vivo, INCB086550 reduced tumor growth in CD34+ humanized mice and induced T-cell activation gene signatures, consistent with PD-L1/PD-1 pathway blockade. Preliminary data from an ongoing phase I study confirmed PD-L1/PD-1 blockade in peripheral blood cells, with increased immune activation and tumor growth control. These data support continued clinical evaluation of INCB086550 as an alternative to antibody-based therapies. SIGNIFICANCE: We have identified a potent small-molecule inhibitor of PD-L1, INCB086550, which has biological properties similar to PD-L1/PD-1 monoclonal antibodies and may represent an alternative to antibody therapy. Preliminary clinical data in patients demonstrated increased immune activation and tumor growth control, which support continued clinical evaluation of this approach. See related commentary by Capparelli and Aplin, p. 1413. This article is highlighted in the In This Issue feature, p. 1397.

Discovery of Pemigatinib: A Potent and Selective Fibroblast Growth Factor Receptor (FGFR) Inhibitor.

Aberrant activation of FGFR has been linked to the pathogenesis of many tumor types. Selective inhibition of FGFR has emerged as a promising approach for cancer treatment. Herein, we describe the discovery of compound 38 (INCB054828, pemigatinib), a highly potent and selective inhibitor of FGFR1, FGFR2, and FGFR3 with excellent physiochemical properties and pharmacokinetic profiles. Pemigatinib has received accelerated approval from the U.S. Food and Drug Administration for the treatment of adults with previously treated, unresectable locally advanced or metastatic cholangiocarcinoma with a FGFR2 fusion or other rearrangement. Additional clinical trials are ongoing to evaluate pemigatinib in patients with FGFR alterations.

INCB054828 (pemigatinib), a potent and selective inhibitor of fibroblast growth factor receptors 1, 2, and 3, displays activity against genetically defined tumor models.

Alterations in fibroblast growth factor receptor (FGFR) genes have been identified as potential driver oncogenes. Pharmacological targeting of FGFRs may therefore provide therapeutic benefit to selected cancer patients, and proof-of-concept has been established in early clinical trials of FGFR inhibitors. Here, we present the molecular structure and preclinical characterization of INCB054828 (pemigatinib), a novel, selective inhibitor of FGFR 1, 2, and 3, currently in phase 2 clinical trials. INCB054828 pharmacokinetics and pharmacodynamics were investigated using cell lines and tumor models, and the antitumor effect of oral INCB054828 was investigated using xenograft tumor models with genetic alterations in FGFR1, 2, or 3. Enzymatic assays with recombinant human FGFR kinases showed potent inhibition of FGFR1, 2, and 3 by INCB054828 (half maximal inhibitory concentration [IC50] 0.4, 0.5, and 1.0 nM, respectively) with weaker activity against FGFR4 (IC50 30 nM). INCB054828 selectively inhibited growth of tumor cell lines with activation of FGFR signaling compared with cell lines lacking FGFR aberrations. The preclinical pharmacokinetic profile suggests target inhibition is achievable by INCB054828 in vivo with low oral doses. INCB054828 suppressed the growth of xenografted tumor models with FGFR1, 2, or 3 alterations as monotherapy, and the combination of INCB054828 with cisplatin provided significant benefit over either single agent, with an acceptable tolerability. The preclinical data presented for INCB054828, together with preliminary clinical observations, support continued investigation in patients with FGFR alterations, such as fusions and activating mutations.

Cardiac contractility: Correction strategies applied to telemetry data from a HESI-sponsored consortium.

INTRODUCTION: QT has a long history of heart rate (HR) correction but limited investigations have been undertaken to assess the impact of cardiovascular parameters on left ventricular (LV) contractility in drug safety testing. Cardiac contractility is affected by preload (Cyon-Frank-Starling law), afterload (Anrep effect) and HR (Bowditch effect). We evaluated multi-parameter correction methods to help with dP/dtmax interpretation. METHODOLOGY: Modeling was undertaken using data from dogs in single or double 4×4 Latin square studies. Correction models (16 fitting formulas×2 modeling approaches (universal and individualized)×2 correction approaches (linear or proportional)) were evaluated. 3D/2D cloud analysis of the beat-to-beat data for the control, pimobendan, and either itraconazole or atenolol groups were used to evaluate correlations between parameters and derive an optimal correction method. RESULTS: Cardiac contractility (i.e., dP/dtmax) was best correlated to HR and systolic LV pressure with a correlation coefficient of 0.8. In decreasing order, dP/dtmin, mean arterial blood pressure (BP), systolic BP, diastolic BP, arterial pulse pressure and LV end diastolic pressure (LVEDP) showed a reduced correlation to dP/dtmax. Subject-specific models improved the correction by up to 14% when compared to universal correction models. The non-linear correction model was superior to the linear model. DISCUSSION: Results suggest that the optimal correction formula for dP/dtmax would be subject-specific, non-linear and would include HR and LV systolic pressure. Correcting contractility for HR and systolic LV pressure may enhance data interpretation in non-clinical drug safety assessments. Similar correction methods could be evaluated for other species used in safety pharmacology.

The Safety Pharmacology Society salary survey.

INTRODUCTION: Safety pharmacology is a growing discipline with scientists broadly distributed across international geographical regions. This electronic salary survey is the first to be distributed amongst the entire Safety Pharmacology Society (SPS) membership. An electronic survey was sent to all members of the Society. Categorical survey questions assessed membership employment types, annual incomes, and professional certifications, along with other associated career attributes. METHODS: This survey was distributed to the SPS membership that is comprised of safety pharmacologists, toxicologists and pharmacologists working globally in the pharmaceutical industry, at contract research organizations (CRO), regulatory agencies, and academia or within the technology provider industry. The survey was open for responses from December 2015 to March 2016. RESULTS: The survey response rate was 28% (129/453). North America (68%) was the region with the largest number of respondents followed by Europe (28%). A preponderance of respondents (77%) had 12years of industry experience or more. 52% of responders earned annually between $40,000 and $120,000. As expected, salary was generally positively correlated with the number of years of experience in the industry or the educational background but there was no correlation between salary and the number of employee's directly supervised. The median salary was higher for male vs female respondents, but so was median age, indicative of no gender 'salary gap'. DISCUSSION: Our 2016 SPS salary survey results showcased significant diversity regarding factors that can influence salary compensation within this discipline. These data provided insights into the complex global job market trends. They also revealed the level of scientific specialization embedded within the organization, presently uniquely positioned to support the dynamic career paths of current and future safety pharmacologists.

Different species require different correction factors for the QT interval.

The ICH S7B guideline specifically requests the evaluation of the QT interval in in vivo models as an accepted risk factor for fatal tachyarrythmias. While it recommends correcting the QT interval for heart rate (HR), it also concedes that such corrections can yield misleading results. Data acquired from 40 cynomolgus monkeys (CM) and 66 Beagle dogs (BD) on 64 and 166 episodes, respectively, of 25-h ECG data collection in healthy control group animals were analyzed for this publication. The total number of ECGs evaluated was 10,761 (CM) and 24,882 (BD). The two species appear to have some difference in cardiac repolarization regulatory mechanisms. CM are more subject to diurnal fluctuations of autonomic nervous tone, which leads to dramatic variation of QT interval duration (up to 12.7%) at the same HR (60 to 70 bpm) in different light cycles. BD do not have such a variation. Different species require different QT correction formulas. Van de Water's correction provides optimal results in BD; Bazett's correction presents optimal results in CM. Fundamental behavioral differences (domesticated vs wild animals) may require individual approaches in the interpretation of the safety pharmacology studies in various species.

Variations in hemodynamic parameters and ECG in healthy, conscious, freely moving telemetrized beagle dogs.

Interpretation of the dynamic cardiovascular parameters on safety pharmacology studies is a challenging process; sometimes, it is difficult to separate normal physiological variations from the effects of the test drug. Data from healthy control Beagle dogs (41 males and 25 females) implanted with telemetry transmitters (DSI, St. Paul, MN) from 34 studies performed from 2003 to 2005 were analyzed. Telemetry data were collected for a 30-s period every 10 min for 24 h after sham dosing. One-hour averages were analyzed. Prior to dosing, heart rate (HR) was 95.6 +/- 26.6 bpm; mean, systolic, and diastolic blood pressure (BP) were 105.3 +/- 12.7, 142.5 +/- 5.3, and 84.7 +/- 11.1 mmHg, respectively. PR, QRS, QT, and corrected (Van de Water) QT intervals were 121 +/- 13, 33 +/- 3, 217 +/- 23, and 245 +/- 18 ms, respectively. Seasonal and slight diurnal patterns were noticed only in HR; BP and body temperature were more stable. PR and QT intervals were inversely related to HR; in addition, the duration of PR was influenced by the light cycle. A comparison of three QT correction formulas demonstrated that Van de Water's formula provided the optimal results in Beagle dogs over a wide range of HR.

The Diplomate in Safety Pharmacology (DSP) certification scheme.

As with other professional disciplines there is a growing need from within industry as well as global regulatory authorities for implementation of a certification process in order to assure that appropriate expertise is developed and quality standards are identified for professionals involved in the practice of Safety Pharmacology (SP). In order to meet this need, the Safety Pharmacology Society (SPS) has developed the Diplomate in Safety Pharmacology (DSP) certification process. There are many benefits to certification including authentication of the discipline within the overall pharmaceutical community and with regulatory authorities. It also encourages participation in SPS activities by other professionals (toxicologists, clinicians, academics) who wish to broaden their professional expertise. It provides an opportunity for candidates to strengthen their fundamental scientific knowledge, and stimulates the sharing of data, methods and model development in the form of publications and presentations on relevant topics in SP. Accreditation in SP occurs after candidates successfully complete a written certification examination conducted at the annual SPS meeting. The DSP exam consists primarily of material pertinent to the conduct of SP vital function core battery studies (i.e., cardiovascular, respiratory and central nervous systems), supplemental SP studies (i.e., renal/urinary, gastrointestinal, immunology, and hematology), Regulatory Guidelines (ICH Guidelines) as well as relevant cross-functional knowledge (e.g., physiology, pharmacology, toxicology, biochemistry, pathology, pharmacokinetics, dosing formulation, analytical methods, and statistics). Maintenance of the DSP certification results from the accrual of credits which are gained from a range of educational and scientific contributions. Eligibility requirements include a combination of at least a bachelor degree in science and two years of relevant professional SP experience and one poster presentation on a SP topic as first author at a recognized major scientific meeting.

Blood compatibility of a newly developed trileaflet mechanical heart valve.

An ideal heart valve prosthesis, which has both the flow dynamic properties and blood compatibility of a tissue valve prosthesis and the durability of a mechanical prosthesis, does not exist. The Triflo trileaflet mechanical heart valve (MHV; Triflo Medical Inc., Irvine, CA) is a newly developed MHV prosthesis with the following design goals: central flow, minimal flow disturbance and stasis around the hinge region, and durability. The current study was conducted to evaluate the blood compatibility of a 29 mm Triflo MHV in the mitral position of eight calves for 5 months without any postoperative anticoagulation. Whole blood platelet aggregometry and the Xylum Clot Signature Analyzer (Xylum Corporation, Scarsdale, NY) were used to evaluate the postoperative changes in platelet and coagulation functions. Full autopsies, histological examinations of major internal organs, and scanning electron microscopy analyses of the explants were performed. Early termination occurred in two cases; one was because of valve thrombosis on the 25th day, and the other was killed because of a nonvalvular complication on the 105th day. The valve thrombosis was attributed to prolonged ventricular fibrillation at the time of valve replacement surgery. Whole blood platelet aggregometry and clot signature analyzer parameters did not show any sign of activation of platelets or the coagulation system. No hemolysis was observed. There was no macroscopic valve thrombosis or embolism observed in the remaining seven cases. Scanning electron microscopy analyses showed clean leaflet and valve ring surfaces, with only occasional minute platelet aggregations. Excellent blood compatibility of the Triflo MHV was demonstrated in this study.

Evaluation of the effect of ruxolitinib on cardiac repolarization: A thorough QT study.

This was a randomized, four-way crossover study that evaluated the effects of placebo, single doses of ruxolitinib 25 and 200 mg, and a single dose of moxifloxacin 400 mg on heart rate-corrected QT interval in healthy subjects. Electrocardiograms (ECGs) and pharmacokinetic samples were obtained on each dosing day; baseline ECGs were taken pre-dose. The primary endpoint was placebo-subtracted change from baseline heart rate-corrected QT (Fridericia formula [ΔΔQTcF]). The ΔΔQTcF for either dose of ruxolitinib ranged from -3.09 to 3.28 milliseconds (1-sided 95% confidence interval of 0.06-6.62 milliseconds). The ΔΔQTcF for moxifloxacin (lower confidence interval) was significantly >5 milliseconds at 1, 2, and 3 hours post-dose. Individual QTcF >450 milliseconds and QTcF from baseline >30 milliseconds following ruxolitinib were similar to placebo. Based on the International Conference on Harmonization E14 guidance, the study results were considered negative for QTc prolongation. In conclusion, ruxolitinib did not have a clinically significant effect on QT interval.

INCB38579, a novel and potent histamine H4 receptor small molecule antagonist with anti-inflammatory pain and anti-pruritic functions.

The histamine H4 receptor mediates several histamine-induced cellular functions of leukocytes, including cell migration and cytokine production. Recent studies suggest that histamine signaling through the histamine H4 receptor can also have anti-pruritic and anti-nociceptive functions. 1-(7-(2-amino-6-(4-methylpiperazin-1-yl) pyrimidin-4-yl)-3, 4-dihdroisoquinolin-2(1H)-yl)-2-cyclopentylethanone (INCB38579) is a novel small molecule antagonist of the human and rodent histamine H4 receptors with at least 80-fold selectivity over the human histamine H1, H2 and H3 receptors, and has good pharmacokinetic properties in rats and mice. The compound is potent in inhibiting histamine binding to and signaling through the recombinant human, mouse and rat histamine H4 receptors and blocks the histamine-induced migration of human and mouse dendritic cells, as well as the cell shape change and migration of human eosinophils. INCB38579 and histamine may have separate but overlapping binding sites on the human histamine H4 receptor. This novel inhibitor is efficacious when evaluated in two previously established in vivo models for histamine H4 receptor activity (histamine-induced itch in mice and carrageenan-induced acute inflammatory pain in rats). When examined in formalin-induced pain models, INCB38579 significantly reduces the sustained inflammatory pain experienced by rats and mice. A good correlation between the protein binding adjusted potency from in vitro studies and its analgesic effect in vivo was observed. These results suggest that INCB38579 can serve as a useful tool for pharmacologic characterization of the histamine H4 receptor and further support the hypothesis that targeting the histamine H4 receptor may provide new therapeutic agents for various chronic inflammatory diseases, including inflammatory pain.