Low muscle mass and sarcopenia: common and predictive of osteopenia in inflammatory bowel disease

BACKGROUND

Body composition is poorly studied in inflammatory bowel disease (IBD). Sarcopenia describes a loss of muscle mass and strength.

AIM

To assess the prevalence of low lean mass (LM), sarcopenia and associated morbidity in an adult IBD cohort.

METHODS

Cross-sectional data were gathered on pre-menopausal 18- to 50-year-old patients with IBD. Whole-body dual-energy X-ray absorptiometry, anthropometric assessment and grip strength were performed. Low LM was defined as ≥1 s.d. below the population mean for appendicular skeletal muscle index [ASMI (kg)/height (m)²], and sarcopenia as both ASMI and grip strength ≥1 s.d. below population mean. Multivariate regression analyses were performed.

RESULTS

Of 137 participants (median age 31 years, BMI 24.8 kg/m(2) ), 56% were male and 69% had Crohn's disease (CD). Low LM and sarcopenia were observed in 21% and 12% of patients, respectively, and osteopenia/osteoporosis in 38% of patients (mean lumbar spine t-score -0.3 ± s.d. 1.1). Grip strength predicted low LM and sarcopenia better than did body mass index (BMI) (OR 4.8 vs. OR 0.7 for low-LM, P < 0.05 both). Normal BMI was falsely reassuring in 72% and 76% of patients with low ASMI and sarcopenia, respectively. Low LM and sarcopenia (OR = 3.6, P = 0.03; OR = 6.3, P = 0.02; respectively), but not BMI nor fat mass, predicted osteopenia/osteoporosis.

CONCLUSIONS

Low lean mass and sarcopenia are common in patients with IBD, and important to recognise as they predict osteopenia/osteoporosis. Grip strength testing should be incorporated into routine clinical practice to detect low lean mass deficits, which may go unrecognised using BMI alone.

The Bcl-2 family antagonist ABT-737 significantly inhibits multiple animal models of autoimmunity

The Bcl-2 family of proteins plays a critical role in controlling immune responses by regulating the expansion and contraction of activated lymphocyte clones by apoptosis. ABT-737, which was originally developed for oncology, is a potent inhibitor of Bcl-2, Bcl-x(L), and Bcl-w protein function. There is evidence that Bcl-2-associated dysregulation of lymphocyte apoptosis may contribute to the pathogenesis of autoimmunity and lead to the development of autoimmune diseases. In this study, we report that ABT-737 treatment resulted in potent inhibition of lymphocyte proliferation as measured by in vitro mitogenic or ex vivo Ag-specific stimulation. More importantly, ABT-737 significantly reduced disease severity in tissue-specific and systemic animal models of autoimmunity. Bcl-2 family antagonism by ABT-737 was efficacious in treating animal models of arthritis and lupus. Our results suggest that treatment with a Bcl-2 family antagonist represents a novel and potentially attractive therapeutic approach for the clinical treatment of autoimmunity.

ABBV-105, a selective and irreversible inhibitor of Bruton's tyrosine kinase, is efficacious in multiple preclinical models of inflammation

OBJECTIVES

Bruton's tyrosine kinase (BTK) is a non-receptor tyrosine kinase required for intracellular signaling downstream of multiple immunoreceptors. We evaluated ABBV-105, a covalent BTK inhibitor, using in vitro and in vivo assays to determine potency, selectivity, and efficacy to validate the therapeutic potential of ABBV-105 in inflammatory disease.

METHODS

ABBV-105 potency and selectivity were evaluated in enzymatic and cellular assays. The impact of ABBV-105 on B cell function in vivo was assessed using mechanistic models of antibody production. Efficacy of ABBV-105 in chronic inflammatory disease was evaluated in animal models of arthritis and lupus. Measurement of BTK occupancy was employed as a target engagement biomarker.

RESULTS

ABBV-105 irreversibly inhibits BTK, demonstrating superior kinome selectivity and is potent in B cell receptor, Fc receptor, and TLR-9-dependent cellular assays. Oral administration resulted in rapid clearance in plasma, but maintenance of BTK splenic occupancy. ABBV-105 inhibited antibody responses to thymus-independent and thymus-dependent antigens, paw swelling and bone destruction in rat collagen induced arthritis, and reduced disease in an IFNα-accelerated lupus nephritis model. BTK occupancy in disease models correlated with in vivo efficacy.

CONCLUSION

ABBV-105, a selective BTK inhibitor, demonstrates compelling efficacy in pre-clinical mechanistic models of antibody production and in models of rheumatoid arthritis and lupus.

Design and Development of Glucocorticoid Receptor Modulators as Immunology Antibody-Drug Conjugate Payloads

Glucocorticoid receptor modulators (GRM) are the first-line treatment for many immune diseases, but unwanted side effects restrict chronic dosing. However, targeted delivery of a GRM payload via an immunology antibody-drug conjugate (iADC) may deliver significant efficacy at doses that do not lead to unwanted side effects. We initiated our α-TNF-GRM ADC project focusing on identifying the optimal payload and a linker that afforded stable attachment to both the payload and antibody, resulting in the identification of the synthetically accessible maleimide-Gly-Ala-Ala linker. DAR 4 purified ADCs were shown to be more efficacious in a mouse contact hypersensitivity model than the parent α-TNF antibody. Analysis of P1NP and corticosterone biomarkers showed there was a sufficient therapeutic window between efficacy and unwanted effects. In a chronic mouse arthritis model, α-TNF-GRM ADCs were more efficacious than both the parent α-TNF mAb and an isotype control bearing the same GRM payload.

Discovery of ABBV-3373, an Anti-TNF Glucocorticoid Receptor Modulator Immunology Antibody Drug Conjugate

Using a convergent synthetic route to enable multiple points of diversity, a series of glucocorticoid receptor modulators (GRM) were profiled for potency, selectivity, and drug-like properties in vitro. Despite covering a large range of diversity, profiling the nonconjugated small molecule was suboptimal and they were conjugated to a mouse antitumor necrosis factor (TNF) antibody using the MP-Ala-Ala linker. Screening of the resulting antibody drug conjugates (ADCs) provided a better assessment of efficacy and physical properties, reinforcing the need to conduct structure-activity relationship studies on the complete ADC. DAR4 ADCs were screened in an acute mouse contact hypersensitivity model measuring biomarkers to ensure a sufficient therapeutic window. In a chronic mouse arthritis model, mouse anti-TNF GRM ADCs were efficacious after a single dose of 10 mg/kg i.p. for over 30 days. Data on the unconjugated payloads and mouse surrogate anti-TNF ADCs identified payload 17 which was conjugated to a human anti-TNF antibody and advanced to the clinic as ABBV-3373.

Development of Orally Efficacious Allosteric Inhibitors of TNFα via Fragment-Based Drug Design

Tumor necrosis factor α (TNFα) is a soluble cytokine that is directly involved in systemic inflammation through the regulation of the intracellular NF-κB and MAPK signaling pathways. The development of biologic drugs that inhibit TNFα has led to improved clinical outcomes for patients with rheumatoid arthritis and other chronic autoimmune diseases; however, TNFα has proven to be difficult to drug with small molecules. Herein, we present a two-phase, fragment-based drug discovery (FBDD) effort in which we first identified isoquinoline fragments that disrupt TNFα ligand-receptor binding through an allosteric desymmetrization mechanism as observed in high-resolution crystal structures. The second phase of discovery focused on the de novo design and optimization of fragments with improved binding efficiency and drug-like properties. The 3-indolinone-based lead presented here displays oral, in vivo efficacy in a mouse glucose-6-phosphate isomerase (GPI)-induced paw swelling model comparable to that seen with a TNFα antibody.

Optimization of Drug-Linker to Enable Long-term Storage of Antibody-Drug Conjugate for Subcutaneous Dosing

To facilitate subcutaneous dosing, biotherapeutics need to exhibit properties that enable high-concentration formulation and long-term stability in the formulation buffer. For antibody-drug conjugates (ADCs), the introduction of drug-linkers can lead to increased hydrophobicity and higher levels of aggregation, which are both detrimental to the properties required for subcutaneous dosing. Herein we show how the physicochemical properties of ADCs could be controlled through the drug-linker chemistry in combination with prodrug chemistry of the payload, and how optimization of these combinations could afford ADCs with significantly improved solution stability. Key to achieving this optimization is the use of an accelerated stress test performed in a minimal formulation buffer.

Inhibition of Interleukin-23-Mediated Inflammation with a Novel Small Molecule Inverse Agonist of RORγt

Blockade of interleukin (IL)-23 or IL-17 with biologics is clinically validated as a treatment of psoriasis. However, the clinical impact of targeting other nodes within the IL-23/IL-17 pathway, especially with small molecules, is less defined. We report on a novel small molecule inverse agonist of retinoid acid-related orphan receptor (ROR) γt and its efficacy in preclinical models of psoriasis and arthritis. 1-(2,4-Dichloro-3-((1,4-dimethyl-6-(trifluoromethyl)-1H-indol-2-yl)methyl)benzoyl)piperidine-4-carboxylic acid (A-9758) was optimized from material identified from a high-throughput screening campaign. A-9758 is selective for RORγt and exhibits robust potency against IL-17A release both in vitro and in vivo. In vivo, we also show that IL-23 is sufficient to drive the accumulation of RORγt+ cells, and inhibition of RORγt significantly attenuates IL-23-driven psoriasiform dermatitis. Therapeutic treatment with A-9758 (i.e., delivered during active disease) was also effective in blocking skin and joint inflammation. Finally, A-9758 exhibited efficacy in an ex vivo human whole blood assay, suggesting small molecule inverse agonists of RORγt could be efficacious in human IL-17-related diseases. SIGNIFICANCE STATEMENT: Using a novel small molecule inverse agonist, and preclinical assays, we show that RORγt is a viable target for the inhibition of RORγt/Th17-driven diseases such as psoriasis. Preclinical models of psoriasis show that inhibition of RORγt blocks both the accumulation and effector function of IL-17-producing T cells.

Discovery of ABBV-154, an anti-TNF Glucocorticoid Receptor Modulator Immunology Antibody-Drug Conjugate (iADC)

Stable attachment of drug-linkers to the antibody is a critical requirement, and for maleimide conjugation to cysteine, it is achieved by ring hydrolysis of the succinimide ring. During ADC profiling in our in-house property screening funnel, we discovered that the succinimide ring open form is in equilibrium with the ring closed succinimide. Bromoacetamide (BrAc) was identified as the optimal replacement, as it affords stable attachment of the drug-linker to the antibody while completely removing the undesired ring open-closed equilibrium. Additionally, BrAc also offers multiple benefits over maleimide, especially with respect to homogeneity of the ADC structure. In combination with a short, hydrophilic linker and phosphate prodrug on the payload, this afforded a stable ADC (ABBV-154) with the desired properties to enable long-term stability to facilitate subcutaneous self-administration.

An anti-TNF-glucocorticoid receptor modulator antibody-drug conjugate is efficacious against immune-mediated inflammatory diseases

Glucocorticoids (GCs) are efficacious drugs used for treating many inflammatory diseases, but the dose and duration of administration are limited because of severe side effects. We therefore sought to identify an approach to selectively target GCs to inflamed tissue. Previous work identified that anti-tumor necrosis factor (TNF) antibodies that bind to transmembrane TNF undergo internalization; therefore, an anti-TNF antibody-drug conjugate (ADC) would be mechanistically similar, where lysosomal catabolism could release a GC receptor modulator (GRM) payload to dampen immune cell activity. Consequently, we have generated an anti-TNF-GRM ADC with the aim of inhibiting pro-inflammatory cytokine production from stimulated human immune cells. In an acute mouse model of contact hypersensitivity, a murine surrogate anti-TNF-GRM ADC inhibited inflammatory responses with minimal effect on systemic GC biomarkers. In addition, in a mouse model of collagen-induced arthritis, single-dose administration of the ADC, delivered at disease onset, was able to completely inhibit arthritis for greater than 30 days, whereas an anti-TNF monoclonal antibody only partially inhibited disease. ADC treatment at the peak of disease was also able to attenuate the arthritic phenotype. Clinical data for a human anti-TNF-GRM ADC (ABBV-3373) from a single ascending dose phase 1 study in healthy volunteers demonstrated antibody-like pharmacokinetic profiles and a lack of impact on serum cortisol concentrations at predicted therapeutic doses. These data suggest that an anti-TNF-GRM ADC may provide improved efficacy beyond anti-TNF alone in immune mediated diseases while minimizing systemic side effects associated with standard GC treatment.

NRF2 activator A-1396076 ameliorates inflammation in autoimmune disease models by inhibiting antigen dependent T cell activation

Nuclear factor (erythroid-derived 2) like 2 (NRF2) is a nuclear transcription factor activated in response to oxidative stress that induces a gene program that dampens inflammation and can limit cell damage that perpetuates the inflammatory response. We have identified A-1396076, a potent and selective NRF2 activator with demonstrated KEAP1 binding and modulation of cellular NRF2 mediated effects. In vivo administration of A-1396076 inhibits inflammation across several rodent models of autoimmunity when administered at or before the time of antigen challenge while also inducing NRF2 modulated gene transcription in the liver of the animals. It was not effective when administered after the time of antigen challenge or in a T cell independent model of arthritis induced by passive transfer of anti-collagen antibodies. A-1396076 inhibited antigen dependent T cell activation as measured by IFN-γ production in an ex vivo re-stimulation assay and following anti-CD3 challenge of MOG-sensitized mice. A-1396076 reduced costimulatory molecule expression on dendritic cells in the lungs of OVA LPS challenged mice suggesting that the mechanism of T cell inhibition was mediated at least partially by interfering with antigen presentation. These data suggest that NRF2 activation may be an effective strategy to dampen inflammation for treatment of autoimmune disease.

Venetoclax (ABT-199), a potent and selective BCL-2 inhibitor, is efficacious in NZB/WF1 mouse model of lupus nephritis and reduces human lymphocyte lifespan in vitro (BA4P.127)

Proteins in the BCL-2 family are key regulators of apoptosis, or programmed cell death. We have conducted studies to evaluate a highly potent and orally available BCL-2 selective inhibitor, venetoclax (ABT-199), for efficacy and mechanism of action in the lupus prone NZB/W F1 mouse model and in human cells in vitro. Venetoclax treatment dose-dependently reduced the incidence of severe proteinuria and prolonged survival compared to vehicle controls and attenuated glomerulonephritis, tubular dilatation, immune cell infiltrates and IgG deposition in the kidney. Venetoclax mediated a significant reduction in the numbers of splenic T cells but conferred a preferential reduction in select B cell subsets. Interestingly, venetoclax did not impair the number of CD138+ long-lived plasma cells in the bone marrow, which was consistent with unaltered circulating anti-dsDNA titers in these animals. Venetoclax efficacy also correlated with a dose -dependent reduction of lymphocytes in peripheral blood of NZB/WF1 mice. Consistent with these findings, human lymphocytes from both healthy donors and systemic lupus erythematosus (SLE) patients treated with venetoclax in vitro have reduced lifespan. Taken together, these data underscore the essential role of BCL-2 in the pathogenesis of lupus and support further exploration of selective BCL-2 inhibition in autoimmune diseases such as SLE/Lupus Nephritis. The design, study conduct, and financial support for this research were provided by AbbVie.

Anti-TNF Thioester Glucocorticoid Antibody-Drug Conjugate Fully Inhibits Inflammation with Minimal Effect on Systemic Corticosterone Levels in a Mouse Arthritis Model

We describe the discovery of a thioester-containing glucocorticoid receptor modulator (GRM) payload and the corresponding antibody-drug conjugate (ADC). Payload 6 was designed for rapid hepatic inactivation to minimize systemic exposure of nonconjugated GRM. Mouse PK indicated that 6 is cleared 10-fold more rapidly than a first-generation GRM payload, resulting in 10-fold lower exposure and 3-fold decrease in Cmax. The anti-mTNF conjugate ADC5 fully inhibited inflammation in mouse contact hypersensitivity with minimal effects on corticosterone, a biomarker for systemic GRM effects, at doses up to and including 100 mg/kg. Concomitant inhibition of P1NP suggests potential delivery to cells involved in the remodeling of bone, which may be a consequence of TNF-targeting or bystander payload effects. Furthermore, ADC5 fully suppressed inflammation in collagen-induced arthritis mouse model after one 10 mg/kg dose for 21 days. The properties of the anti-hTNF conjugate were suitable for liquid formulation and may enable subcutaneous dosing.

Soy Protein Containing Diet Attenuates Murine Drug Exposure and Activity via Hepatic and Intestinal Cytochrome P450 Induction

Pharmacokinetic variability in drug plasma exposure between different studies within the same species is not unexpected due to a variety of factors (such as differences in formulation, active pharmaceutical ingredient salt form and solid-state, genetic strain, sex, environmental, disease status, bioanalysis methods, circadian rhythms, etc.) although variability from within the same research group typically does not occur to a great degree because these variables are commonly controlled. Surprisingly, a pharmacology proof of concept study with a previously validated tool compound from the literature failed to show expected response in murine glucose-6-phosphate isomerase-induced arthritis model which was tied to compound plasma exposure unexpectedly 10-fold lower than exposure observed from early pharmacokinetic study confirming adequate exposure prior to proof of concept. A systematic series of studies were conducted to investigate causes for exposure difference between pharmacology and pharmacokinetic studies identifying the presence or absence of soy protein in animal chow as the causative variable. Cyp3a11 expression in intestine and liver was determined to increase in a time dependent manner in mice switched to diets containing soybean meal compared with mice on diets without soybean meal. The repeated pharmacology experiments using the soybean meal free diet achieved plasma exposures that were maintained above the EC50 and showed efficacy and proof of concept for the target. This effect was further confirmed with marker CYP3A4 substrates in follow on mouse studies. The role of soy protein containing diets on CYP expression necessitates the inclusion of controlling rodent diet as a variable for preventing possible exposure differences between studies. SIGNIFICANCE STATEMENT: The presence of soybean meal protein in murine diet increased clearance and decreased oral exposure for select cytochrome 3A4 substrates. Related effects were also observed on select liver enzyme expression.

IL-23, IFN-α, and IFN-β in the vaginal fluid of patients suffering from vulvovaginal candidosis

Purpose of the investigation: Vulvovaginal candidosis (VVC) is a common vaginal infection affecting almost 75% of all women once per lifetime. Vaginal associated immunity is important in the protection against VVC. The purpose of this study was to evaluate a potential role of IL-23, IFN-α, and IFN-β in the local immune response against VVC.

MATERIALS AND METHODS

The study included 202 non-pregnant women; 71 patients with clinical symptoms of VVC and 131 asymptomatic patients served as control. IL-23, IFN-α, and IFN-β were measured in the vaginal fluid by ELISA. Microbiological cultures were used for Candida detection.

RESULTS

C. albicans was detected in 67.6% of patients, C. glabrata in 2 1.1% of patients, and 5.6% were infected with C. krusei or coinfected with C. albicans and C. krusei. Levels of IL-23 (p < 0.001) and IFN-β (p < 0.017) were significantly lower in the VVC group. IFN-α was elevated in the VVC group compared to the asymptomatic patients (p < 0.001).

CONCLUSION

IL-23 and IEFN-β seem to play a protective role against VVC. Decreased levels in VVC patients suggest a compromised local immune response at the time of occurrence of symptoms. In contrast, IFN-α seems to be released once the infection has occurred. These cytokines may be prospective targets in the treatment and prevention of primary and recurrent vaginal infections with Candida species.

Kinetics of knee synovial lavage inflammation in rodent models of collagen induced arthritis. (171.15)

Rheumatoid arthritis (RA) is an autoimmune disease characterized by inflammation, swelling, and destruction of joints. In this study we used intra-articular lavage of the knee joint to easily and rapidly assess the kinetics of cellular infiltration and cytokine production within the local joint synovial environment during disease in rodent models of arthritis. In collagen induced arthritis in rats, knees of arthritic animals had increased cellularity composed of neutrophils, monocytes and T cells as well as marked increases in pro-inflammatory cytokines and chemokines including IL-1b, IL-6, and KC. The kinetics of infiltration showed an initial infiltration of monocytes shortly followed by a significant increase in neutrophil infiltration that strongly correlated with paw swelling. CD4+ T cells increased as well, but were not found in high numbers in the joint until after maximal paw swelling had been reached. We also found that the influx of monocytes into the knee joint space correlated with increased levels of KC, IL-1b, and IL-6, with KC levels preceding the subsequent neutrophil influx. Mouse models show similar disease course in regards to both inflammation and cytokine production in the synovial knee lavage. Understanding the kinetics of disease in the local joint presents new opportunities for biomarker development, target identification, and improvement of mechanistic understanding of disease processes in rodent models of arthritis.

Pain and inflammation coincide in a collagen-induced arthritis model in rats (171.17)

Rheumatoid arthritis (RA) is an autoimmune disease characterized by joint inflammation, swelling and destruction. In patients diagnosed with RA, these symptoms manifest as pain and lead to fatigue, physical impairment and loss of function. This can be modeled pre-clinically using collagen induced arthritis (rat CIA). Historically, increased swelling of the hind paws measured by plethysmography, and inflammation measured by histology in the ankle joints of arthritic rats have been used to evaluate the effects of potential anti-inflammatory therapies. In the present study, we set out to understand the relationship between joint inflammation and pain. To evaluate knee inflammation, we employed a technique that involves lavaging the knee joint to determine the characteristics of the inflammation (cells and cytokines). Knees of arthritic animals had increased cellularity and pro-inflammatory cytokines including IL-1b and IL-6, as well as increases in the neutrophil chemokine KC. To evaluate pain, we used Von Frey monofilaments to elicit mechanical allodynia as measured by paw withdrawal. We initially observed increased paw withdrawal activity on day 11, with maximal pain responses by day 15 that were maintained through day 18. These findings indicate that mechanisms of pain and inflammation are coordinate in the rat CIA model. Measurement of pain in preclinical models of RA will aid in the development of future effective therapies.

Abstract P3-13-02: Surcigal management of ipsilateral breast tumor recurrence

PURPOSE

Approximately 10-15% of breast cancer patients treated by breast conserving surgery (BCS) and adjuvant radiotherapy (RT) will develop ipsilateral breast tumor recurrence (IBTR).

International guidelines suggest total mastectomy as treatment of choice for IBTR following lumpectomy and RT. Nevertheless, there is evidence that second BCS might be equally sufficient.

PATIENTS AND METHODS

Patients with IBTR diagnosed between 1990 and 2014 after BCS and RT were included (n=170).

34.1% women underwent secondary BCS, whereas 65.9% were treated by mastectomy. We determined predictive factors for time to local progression (TTP), disease free survival (DFS), and overall survival (OS) comparing these two groups.

RESULTS

Median follow-up after primary IBTR was 49 months (59 months for patients still alive at time of analysis). Five-year IBTR-free rate after secondary BCS was 77.6% (SD±6.1%) and 75.0% (SD±4.5%) for patients after mastectomy. Five-year DFS was 57.3% (SD±8.2%), and 61.9% (SD±5.5%), five-year OS was 84.7% (SD±5.8%), and 72.6% (SD±5.1%), respectively.

Prior adjuvant systemic therapy, muscular invasion, and skin infiltration were independent significant risk factors for a shorter TTP.

Additionally, lymphovascular infiltration (LVI) in the IBTR increased the risk for a shorter DFS.

LVI, muscular invasion, and skin infiltration were identified as independent significant risk factors for a shorter OS.

CONCLUSION

No significant difference in local control, DFS, and OS was seen between IBTR patients treated either by secondary BCS or mastectomy. Our data suggest that secondary BCS for IBTR patients after initial BCS and RT is feasible in selected patients.

Citation Format: Kolben T, Schwarz TM, Goess C, Blume C, Degenhardt T, Engel J, Wuerstlein R, Ditsch N, Harbeck N, Kahlert S. Surcigal management of ipsilateral breast tumor recurrence. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P3-13-02.

Small molecule interleukin (IL) 17A/A antagonists and antibodies blocking both IL17A/A and IL17A/F demonstrate equivalent degrees of efficacy in preclinical models of skin and joint inflammation

T-helper 17 (Th17) cells produce homodimeric IL17A/A and IL17F/F cytokines as well as the heterodimeric IL17A/F isoform, all having well known roles in defense against extracellular pathogens including fungal infection. Antibodies targeting IL17A (such as secukinumab and ixekizumab) have been approved to treat psoriasis, psoriatic arthritis, ankylosing spondylitis, and axial spondyloarthritis and are under further investigation as therapies in inflammatory disorders such as hidradenitis suppurativa and giant cell arteritis. Because many patients dislike injections with needles, orally bioavailable small molecule IL17 antagonists are desirable as next-generation drugs as long as they can replicate the degree of efficacy observed with anti-IL17A biologics. We recently described novel small molecules binding as 2 copies to the IL17A/A homodimer with only weak effects on the IL17A/F heterodimer. Because approved antibodies binding IL17A neutralize both IL17A/A and IL17A/F, we assessed whether targeting IL17A/A would be sufficient to bring efficacy comparable to IL17A biologics. In comparison to IL17A/F and IL17F/F, we found that the IL17A/A homodimer is the strongest initiator of signaling and that comparable IL17A/A to IL17A/F ratios are expressed in Th17 cells and in human psoriatic skin tissue. Furthermore, our IL17A/A-specific small molecules block the effects of Th17 cell supernatants on keratinocytes to similar maximal responses as anti-IL17A. Our IL17A/A-selective antagonists deliver comparable efficacy to anti-IL17A biologics in several rodent inflammatory models of psoriasiform dermatitis and arthritis. These results support neutralizing IL17A/A with oral small molecule antagonists is an attractive approach to provide differentiated, next-generation therapies for inflammatory disorders. SIGNIFICANCE STATEMENT: This study found that orally active small molecule antagonists of the proinflammatory cytokine IL17A that preferentially bind the IL17A/A form produced equivalent efficacy to monoclonal antibodies that can neutralize both IL17A/A and IL17A/F. This indicates that the IL17A/A homodimer is the dominant isoform driving inflammation in diseases such as psoriasis and that oral inhibitors targeting IL17A/A may be useful next-generation IL17 therapeutics.