A Novel Transmembrane CXCR4 Variant That Expands the WHIM Genotype-Phenotype Paradigm.

Warts, Hypogammglobulinemia, Infections, Myelokathexis (WHIM) syndrome is a rare immunodeficiency disease that results from impaired leukocyte trafficking (myelokathexis) predominately caused by gain-of-function variants in C-X-C chemokine receptor type 4 (CXCR4). Clinical manifestations of WHIM syndrome can differ in familial forms or in people harboring identical CXCR4 variants. All known pathogenic CXCR4 variants associated with WHIM syndrome (CXCR4WHIM) to date are localized in the intracellular C-terminus of CXCR4. We identified 4 unrelated patients with variable WHIM-like clinical presentations harboring a novel heterozygous CXCR4 variant (c.250G>C; p.D84H) localized at a highly conserved position in the transmembrane domain of the receptor outside the C-terminus. Functional characterization of the CXCR4D84Hvariant (CXCR4D84H) using patient-derived peripheral blood mononuclear cells and in vitro cellular assaysshow decreased CXCR4 internalization and increased chemotaxis in response to CXCL12, similar to known CXCR4WHIM, but also revealed unique features of CXCR4D84H signaling to cAMP, Ca2+ mobilization and AKT/ERK pathways. These findings are consistent with molecular dynamics simulations that show disruption of the Na+ binding pocket by D84H, resulting in collapse of the hydrophobic gate above and destabilization of the inactive state of CXCR4. Mavorixafor, a CXCR4 antagonist being evaluated in clinical trials for chronic neutropenia and WHIM syndrome, normalized CXCL12-mediated chemotaxis of CXCR4D84H patient lymphocytes ex vivo and improved WBC and subset counts in 1 patient with CXCR4D84H enrolled in the chronic neutropenia phase 1b clinical trial (NCT04154488). The present study expands the current understanding of CXCR4 function and genotype-phenotype correlations in WHIM syndrome and in people with WHIM-like phenotypes.

Phase 3 randomized trial of mavorixafor, CXCR4 antagonist, in WHIM syndrome.

We investigated efficacy and safety of mavorixafor, an oral CXCR4 antagonist for participants with Warts, Hypogammaglobulinemia, Infections, and Myelokathexis (WHIM) syndrome, a rare immunodeficiency caused by CXCR4 gain-of-function variants. This randomized (1:1), double-blind, placebo-controlled, phase 3 trial enrolled participants aged ≥12 years with WHIM syndrome and absolute neutrophil count (ANC) ≤400/µL. Participants received once-daily mavorixafor or placebo for 52 weeks. Primary endpoint was time (hours) above ANC threshold ≥500/µL (TATANC; over 24 hours). Secondary endpoints included TAT absolute lymphocyte count ≥1000/µL (TATALC; defined similar to TATANC); absolute changes in white blood cell (WBC), ANC, and ALC from baseline; annualized infection rate; infection duration and total infection score (combined infection number/severity). In 31 participants (mavorixafor, n=14; placebo, n=17), mavorixafor least squares (LS) mean TATANC was 15.0 hours, placebo 2.8 hours (P<0.001). Mavorixafor LS mean TATALC was 15.8 hours, placebo 4.6 hours (P<0.001). Higher absolute WBC, ANC, and ALC levels were seen with mavorixafor than placebo at each timepoint assessed. Annualized infection rates were 60% lower with mavorixafor versus placebo (LS mean 1.7 versus 4.2; nominal P=0.007) and total infection scores were 40% lower (7.4 [95% CI, 1.6-13.2] versus 12.3 [95% CI, 7.2-17.3]). Treatment with mavorixafor reduced infection frequency, severity, duration, and antibiotic use. No discontinuations occurred due to treatment-emergent adverse events (TEAEs); no related serious TEAEs were observed. Overall, mavorixafor-treated participants showed significant increases in LS mean TATANC and TATALC, reduced infection frequency, severity/duration. Mavorixafor was well tolerated in participants with WHIM syndrome. Trial was registered at ClinicalTrials.gov NCT03995108.

Genotype-phenotype correlations in WHIM syndrome: a systematic characterization of CXCR4WHIM variants.

Warts, hypogammaglobulinemia, infections, myelokathexis (WHIM) syndrome is a rare primary immunodeficiency predominantly caused by heterozygous gain-of-function mutations in CXCR4 C-terminus. We assessed genotype-phenotype correlations for known pathogenic CXCR4 variants and in vitro response of each variant to mavorixafor, an investigational CXCR4 antagonist. We used cell-based assays to analyze CXCL12-induced receptor trafficking and downstream signaling of 14 pathogenic CXCR4 variants previously identified in patients with WHIM syndrome. All CXCR4 variants displayed impaired receptor trafficking, hyperactive downstream signaling, and enhanced chemotaxis in response to CXCL12. Mavorixafor inhibited CXCL12-dependent signaling and hyperactivation in cells harboring CXCR4WHIM mutations. A strong correlation was found between CXCR4 internalization defect and severity of blood leukocytopenias and infection susceptibility, and between AKT activation and immunoglobulin A level and CD4+ T-cell counts. This study is the first to show WHIM syndrome clinical phenotype variability as a function of both CXCR4WHIM genotype diversity and associated functional dysregulation. Our findings suggest that CXCR4 internalization may be used to assess the pathogenicity of CXCR4 variants in vitro and also as a potential WHIM-related disease biomarker. The investigational CXCR4 antagonist mavorixafor inhibited CXCL12-dependent signaling in all tested CXCR4-variant cell lines at clinically relevant concentrations.

BIIB042, a novel γ-secretase modulator, reduces amyloidogenic Aß isoforms in primates and rodents and plaque pathology in a mouse model of Alzheimer's disease.

Reducing the production of larger aggregation-prone amyloid ß-peptides (Aß) remains an untested therapeutic approach for reducing the appearance and growth of Aß plaques in the brain, which are a hallmark pathological feature of Alzheimer's disease. γ-Secretase modulators (GSMs) are therapeutics that impact γ-secretase-dependent cleavage of amyloid precursor protein to promote the production of shorter Aß peptides that are less prone to aggregation and plaque deposition. This is accomplished without inhibiting overall γ-secretase function and cleavage of other substrates, which is believed to be a source of deleterious side effects. Here, we report the pharmacokinetic and pharmacodynamic properties of BIIB042, a novel bioavailable and brain-penetrant GSM. In cell-based assays, BIIB042 reduced the levels of Aß42, increased the levels of Aß38 and had little effect on the levels of Aß40, the most abundant Aß species. Similar pharmacodynamic properties were confirmed in the central nervous system and in plasma of mice and rats, and also in plasma of cynomolgus monkeys after a single oral dose of BIIB042. BIIB042 reduced Aß42 levels and Aß plaque burden in Tg2576 mice, which overexpress human amyloid precursor protein and serve as a model system for Alzheimer's disease. BIIB042 did not inhibit cleavage of other γ-secretase substrates in cell-based and in vivo signaling and cleavage assays. The pharmacodynamic effects of lowering Aß42 in the central nervous system coupled with demonstrated efficacy in reducing plaque pathology suggests modulation of γ-secretase, with molecules like BIIB042, is a compelling therapeutic approach for the treatment of Alzheimer's disease.

Discovery and evaluation of a non-Zn chelating, selective matrix metalloproteinase 13 (MMP-13) inhibitor for potential intra-articular treatment of osteoarthritis.

Osteoarthritis (OA) is a nonsystemic disease for which no oral or parenteral disease-modifying osteoarthritic drug (DMOAD) is currently available. Matrix metalloproteinase 13 (MMP-13) has attracted attention as a target with disease-modifying potential because of its major role in tissue destruction associated with OA. Being localized to one or a few joints, OA is amenable to intra-articular (IA) therapy, which has distinct advantages over oral therapies in terms of increasing therapeutic index, by maximizing drug delivery to cartilage and minimizing systemic exposure. Here we report on the synthesis and biological evaluation of a non-zinc binding MMP-13 selective inhibitor, 4-methyl-1-(S)-({5-[(3-oxo-3,4-dihydro-2H-benzo[1,4]oxazin-6-ylmethyl)carbamoyl]pyrazolo[1,5-a]pyrimidine-7-carbonyl}amino)indan-5-carboxylic acid (1), that is uniquely suited as a potential IA-DMOAD: it has long durability in the joint, penetrates cartilage effectively, exhibits nearly no detectable systemic exposure, and has remarkable efficacy.

Discovery of 4-aminomethylphenylacetic acids as γ-secretase modulators via a scaffold design approach.

Starting from literature examples of nonsteroidal anti-inflammatory drugs (NSAIDs)-type carboxylic acid γ-secretase modulators (GSMs) and using a scaffold design approach, we identified 4-aminomethylphenylacetic acid 4 with a desirable γ-secretase modulation profile. Scaffold optimization led to the discovery of a novel chemical series, represented by 6b, having improved brain penetration. Further SAR studies provided analog 6q that exhibited a good pharmacological profile. Oral administration of 6q significantly reduced brain Aß42 levels in mice and rats.

Design, synthesis, and biological evaluation of pyrazolopyrimidine-sulfonamides as potent multiple-mitotic kinase (MMK) inhibitors (part I).

A novel class of pyrazolopyrimidine-sulfonamides was discovered as selective dual inhibitors of aurora kinase A (AKA) and cyclin-dependent kinase 1 (CDK1). These inhibitors were originally designed based on an early lead (compound I). SAR development has led to the discovery of potent inhibitors with single digit nM IC(50)s towards both AKA and CDK1. An exemplary compound 1a has demonstrated good efficacy in an HCT116 colon cancer xenograft model.

Discovery of BIIB042, a Potent, Selective, and Orally Bioavailable γ-Secretase Modulator.

We have investigated a novel series of acid-derived γ-secretase modulators as a potential treatment of Alzheimer's disease. Optimization based on cellular potency and brain pharmacodynamics after oral dosing led to the discovery of 10a (BIIB042). Compound 10a is a potent γ-secretase modulator, which lowered Aß42, increased Aß38, but had little to no effect on Aß40 levels both in vitro and in vivo. In addition, compound 10a did not affect Notch signaling in our in vitro assessment. Compound 10a demonstrated excellent pharmacokinetic parameters in multiple species. Oral administration of 10a significantly reduced brain Aß42 levels in CF-1 mice and Fischer rats, as well as plasma Aß42 levels in cynomolgus monkeys. Compound 10a was selected as a candidate for preclinical safety evaluation.

Diaminocyclobutenediones as potent and orally bioavailable CXCR2 receptor antagonists: SAR in the phenolic amide region.

A series of potent and orally bioavailable 3,4-diaminocyclobutenediones with various amide modifications and substitution on the left side phenyl ring were prepared and found to show significant inhibitory activities towards both CXCR2 and CXCR1 receptors.

3,4-Diamino-1,2,5-thiadiazole as potent and selective CXCR2 antagonists.

A series of potent and selective 3,4-diamino-1,2,5-thiadiazoles were prepared and found to show excellent binding affinities towards CXCR2 receptor.

Fluoroalkyl alpha side chain containing 3,4-diamino-cyclobutenediones as potent and orally bioavailable CXCR2-CXCR1 dual antagonists.

A series of potent and orally bioavailable 3,4-diaminocyclobutenediones with various fluoroalkyl groups as alpha side chain were prepared and found to show significant improvements in the binding affinities towards both CXCR2 and CXCR1 receptors.

Extra binding region induced by non-zinc chelating inhibitors into the S1' subsite of matrix metalloproteinase 8 (MMP-8).

The mode of binding and the activity of the first two non-zinc chelating, potent, and selective inhibitors of human neutrophil collagenase are reported. The crystal structures of the catalytic domain of MMP-8, respectively complexed with each inhibitor, reveals that both ligands are deeply inserted into the primary specificity subsite S(1)', where they induce a similar conformational change of the surrounding loop that is endowed with the main specificity determinants of MMPs. Accord to this rearrangement, both inhibitors remove the floor of the pocket formed by the Y227 side-chain, rendering available an extra binding region never explored before. The present data show that potent and more selective inhibitors can be obtained by developing ligands able to interact with the selectivity regions of the enzyme rather than with the catalytic zinc ion, which is the common feature of all MMP members.

Synthesis and structure-activity relationships of new disubstituted phenyl-containing 3,4-diamino-3-cyclobutene-1,2-diones as CXCR2 receptor antagonists.

A series of 3,4- and 3,5-disubstituted phenyl-containing cyclobutenedione analogues were synthesized and evaluated as CXCR2 receptor antagonists. Variations in the disubstitution pattern of the phenyl ring afforded new compounds with potent CXCR2 binding affinity in the low nanomolar ranges. Moreover, two potent compounds 19 and 26 exhibited good oral pharmacokinetic profiles.

C(4)-alkyl substituted furanyl cyclobutenediones as potent, orally bioavailable CXCR2 and CXCR1 receptor antagonists.

A novel series of cyclobutenedione centered C(4)-alkyl substituted furanyl analogs was developed as potent CXCR2 and CXCR1 antagonists. Compound 16 exhibits potent inhibitory activities against IL-8 binding to the receptors (CXCR2 Ki=1 nM, IC(50)=1.3 nM; CXCR1 Ki=3 nM, IC(50)=7.3 nM), and demonstrates potent inhibition against both Gro-alpha and IL-8 induced hPMN migration (chemotaxis: CXCR2 IC(50)=0.5 nM, CXCR1 IC(50)=37 nM). In addition, 16 has shown good oral pharmacokinetic profiles in rat, mouse, monkey, and dog.

Discovery of 2-hydroxy-N,N-dimethyl-3-{2-[[(R)-1-(5- methylfuran-2-yl)propyl]amino]-3,4-dioxocyclobut-1-enylamino}benzamide (SCH 527123): a potent, orally bioavailable CXCR2/CXCR1 receptor antagonist.

Structure-activity studies on lead cyclobutenedione 3 led to the discovery of 4 (SCH 527123), a potent, orally bioavailable CXCR2/CXCR1 receptor antagonist with excellent cell-based activity. Compound 4 displayed good oral bioavailability in rat and may be a potential therapeutic agent for the treatment of various inflammatory diseases.

Synthesis and structure-activity relationships of 3,4-diaminocyclobut-3-ene-1,2-dione CXCR2 antagonists.

A novel series of 3,4-diaminocyclobut-3-ene-1,2-diones was prepared and found to show potent inhibitory activity of CXCR2 binding and IL-8-mediated chemotaxis of a CXCR2-expressing cell line. Microsome stability and Caco2 studies were subsequently used to show that compounds of this chemotype are predicted to have good oral bioavailability and are thus suitable for pharmaceutical development.

Sch-66336 (sarasar) and other benzocycloheptapyridyl farnesyl protein transferase inhibitors: discovery, biology and clinical observations.

Farnesyl Protein Transferase as a target for therapeutic intervention is currently under investigation in human clinical trials. Sch-66336 (sarasar), a benzocycloheptapyridyl Farnesyl Transferase Inhibitor (FTI), has been found to be effective in cellular proliferation assays and in in vivo oncology models both as a single agent and in combination with other anti-cancer agents. Clinically, early evidence is being generated that suggests efficacy in humans, particularly in patients with leukemia. Herein, we review the biology of FPT, the discovery of Sch-66336 and other benzocycloheptapyridyl FTIs, and the clinical evaluation of Sch-66336 for the treatment of leukemia and solid tumors.

Exploring the role of bromine at C(10) of (+)-4-[2-[4-(8-chloro-3,10-dibromo- 6,11-dihydro-5H-benzo[5,6]cyclohepta[1,2-b]pyridin-11(R)-yl)-1-piperidinyl]-2- oxoethyl]-1-piperidinecarboxamide (Sch-66336): the discovery of indolocycloheptapyridine inhibitors of farnesyl protein transferase.

The 10-bromobenzocycloheptapyridyl farnesyl transferase inhibitor (FTI) Sch-66336 (1) is currently under clinical evaluation for the treatment of human cancers. During structure-activity relationship development leading to 1, 10-bromobenzocycloheptapyridyl FTIs were found to be more potent than analogous compounds lacking the 10-Br substituent. This potency enhancement was believed to be due, in part, to an increase in conformational rigidity as the 10-bromo substituent could restrict the conformation of the appended C(11) piperidyl substituent in an axial orientation. A novel and potent class of FTIs, represented by indolocycloheptapyridine Sch-207758 [(+)-10a], have been designed based on this principle. Although structural and thermodynamic results suggest that entropy plays a crucial role in the increased potency observed with (+)-10a through conformational constraints and solvation effects, the results also indicate that the indolocycloheptapyridine moiety in (+)-10a provides increased hydrophobic interactions with the protein through the addition of the indole group. This report details the X-ray structure and the thermodynamic and pharmacokinetic profiles of (+)-10a, as well as the synthesis of indolocycloheptapyridine FTIs and their potencies in biochemical and biological assays.