R2R01: A long-acting single-chain peptide agonist of RXFP1 for renal and cardiovascular diseases.

BACKGROUND: The therapeutic potential of relaxin for heart failure and renal disease in clinical trials is hampered by the short half-life of serelaxin. Optimization of fatty acid-acetylated single-chain peptide analogues of relaxin culminated in the design and synthesis of R2R01, a potent and selective RXFP1 agonist with subcutaneous bioavailability and extended half-life. EXPERIMENTAL APPROACH: Cellular assays and pharmacological models of RXFP1 activation were used to validate the potency and selectivity of R2R01. Increased renal blood flow was used as a translational marker of R2R01 activity. Human mastocytes (LAD2 cells) were used to study potential pseudo-allergic reactions and CD4+ T-cells to study immunogenicity. The pharmacokinetics of R2R01 were characterized in rats and minipigs. KEY RESULTS: In vitro, R2R01 had comparable potency and efficacy to relaxin as an agonist for human RXFP1. In vivo, subcutaneous administration of R2R01 increased heart rate and renal blood flow in normotensive and hypertensive rat and did not show evidence of tachyphylaxis. R2R01 also increased nipple length in rats, used as a chronic model of RXFP1 engagement. Pharmacokinetic studies showed that R2R01 has a significantly extended terminal half-life. The in vitro assays with LAD2 cells and CD4+ T-cells showed that R2R01 had low potential for pseudo-allergic and immunogenic reactions, respectively. CONCLUSION AND IMPLICATIONS: R2R01 is a potent RXFP1 agonist with an extended half-life that increases renal blood flow in various settings including normotensive and hypertensive conditions. The preclinical efficacy and safety data supported clinical development of R2R01 as a potential new therapy for renal and cardiovascular diseases.

microRNA blood signature for localized radiation injury.

A radiological accident, whether from industrial, medical, or malicious origin, may result in localized exposure to high doses of ionizing radiations, leading to the development of local radiation injury (LRI), that may evolve toward deep ulceration and necrosis of the skin and underlying tissues. Early diagnosis is therefore crucial to facilitate identification and management of LRI victims. Circulating microRNAs (miRNA) have been studied as potential diagnostic biomarkers of several diseases including hematological defects following whole-body irradiation (WBI). This study aims to identify a blood miRNA signature associated with LRI in a preclinical C57BL/6J mouse model of hindlimb irradiation using different 10-MV X-ray doses that lead to injuries of different severities. To this end, we first performed broad-spectrum plasma miRNA profiling, followed by a targeted validation step, on two independent animal cohorts. Using a multivariate sparse partial least square discriminant analysis, we identified a panel of eight circulating miRNAs able to segregate mice according to LRI severity. Interestingly, these miRNAs were previously associated with WBI (miR-150-5p, miR-342-3p, miR-146a-5p), inflammation (miR-18a-5p, miR-148b-3p, miR-532-5p) and skin diseases (miR-139-5p, miR-195-5p). Our results suggest the use of circulating miRNAs as suitable molecular biomarkers for LRI prognosis and diagnosis.

Fatty acid acylated peptide therapeutics: discovery of omega-n oxidation of the lipid chain as a novel metabolic pathway in preclinical species.

We recently described C18 fatty acid acylated peptides as a new class of potent long-lasting single-chain RXFP1 agonists that displayed relaxin-like activities in vivo. Early pharmacokinetics and toxicological studies of these stearic acid acylated peptides revealed a relevant oxidative metabolism occurring in dog and minipig, and also seen at a lower extent in monkey and rat. Mass spectrometry combined to NMR spectroscopy studies revealed that the oxidation occurred, unexpectedly, on the stearic acid chain at ω-1, ω-2 and ω-3 positions. Structure-metabolism relationship studies on acylated analogues with different fatty acids lengths (C15-C20) showed that the extent of oxidation was higher with longer chains. The oxidized metabolites could be generated in vitro using liver microsomes and engineered bacterial CYPs. These systems were correlating poorly with in vivo metabolism observed across species; however, the results suggest that this biotransformation pathway might be catalyzed by some unknown CYP enzymes.

Characterization of a new potent and long-lasting single chain peptide agonist of RXFP1 in cells and in vivo translational models.

Despite beneficial effects in acute heart failure, the full therapeutic potential of recombinant relaxin-2 has been hampered by its short half-life and the need for intravenous administration limiting its use to intensive care units. A multiparametric optimization of the relaxin B-chain led to the identification of single chain lipidated peptide agonists of RXFP1 like SA10SC-RLX with subcutaneous bioavailability and extended half-life. SA10SC-RLX has sub nanomolar activity on cells expressing human RXFP1 and molecular modeling associated with the study of different RXFP1 mutants was used to decipher the mechanism of SA10SC-RLX interaction with RXFP1. Telemetry was performed in rat where SA10SC-RLX was able to engage RXFP1 after subcutaneous administration without tachyphylaxis after repeated dosing. Renal blood flow was then used as a translational model to evaluate RXFP1 activation. SA10SC-RLX increased renal blood flow and decreased renal vascular resistance in rats as reported for relaxin in humans. In conclusion, SA10SC-RLX mimics relaxin activity in in vitro and in vivo models of acute RXFP1 engagement. SA10SC-RLX represents a new class of long-lasting RXFP1 agonist, suitable for once daily subcutaneous administration in patients and potentially paving the way to new treatments for chronic fibrotic and cardiovascular diseases.

Introduction of Non-natural Amino Acids Into T-Cell Epitopes to Mitigate Peptide-Specific T-Cell Responses.

Non-natural modifications are widely introduced into peptides to improve their therapeutic efficacy, but their impact on immunogenicity remains largely unknown. As the CD4 T-cell response is a key factor in triggering immunogenicity, we investigated the effect of introducing D-amino acids (Daa), amino isobutyric acid (Aib), N-methylation, Cα-methylation, reduced amide, and peptoid bonds into an immunoprevalent T-cell epitope on binding to a set of HLA-DR molecules, recognition, and priming of human T cells. Modifications are differentially accepted at multiple positions, but are all tolerated in the flanking regions. Introduction of Aib and Daa in the binding core had the most deleterious effect on binding to HLA-DR molecules and T-cell activation. Their introduction at the positions close to the P1 anchor residue abolished T-cell priming, suggesting they might be sufficient to dampen peptide immunogenicity. Other modifications led to variable effects on binding to HLA-DR molecules and T-cell reactivity, but none exhibited an increased ability to stimulate T cells. Altogether, non-natural modifications appear generally to diminish binding to HLA-DR molecules and hence T-cell stimulation. These data might guide the design of therapeutic peptides to make them less immunogenic.

Identification of Potent and Long-Acting Single-Chain Peptide Mimetics of Human Relaxin-2 for Cardiovascular Diseases.

The insulin-like peptide human relaxin-2 was identified as a hormone that, among other biological functions, mediates the hemodynamic changes occurring during pregnancy. Recombinant relaxin-2 (serelaxin) has shown beneficial effects in acute heart failure, but its full therapeutic potential has been hampered by its short half-life and the need for intravenous administration limiting its use to intensive care units. In this study, we report the development of long-acting potent single-chain relaxin peptide mimetics. Modifications in the B-chain of relaxin, such as the introduction of specific mutations and the trimming of the sequence to an optimal size, resulted in potent, structurally simplified peptide agonists of the relaxin receptor Relaxin Family Peptide Receptor 1 (RXFP1) (e.g., 54). Introduction of suitable spacers and fatty acids led to the identification of single-chain lipidated peptide agonists of RXFP1, with sub-nanomolar activity, high subcutaneous bioavailability, extended half-lives, and in vivo efficacy (e.g., 64).

Translational engagement of lysophosphatidic acid receptor 1 in skin fibrosis: from dermal fibroblasts of patients with scleroderma to tight skin 1 mouse.

BACKGROUND AND PURPOSE: Genetic deletion and pharmacological studies suggest a role for lysophosphatidic acid (LPA1 ) receptor in fibrosis. We investigated the therapeutic potential in systemic sclerosis (SSc) of a new orally active selective LPA1 receptor antagonist using dermal fibroblasts from patients and an animal model of skin fibrosis. EXPERIMENTAL APPROACH: Dermal fibroblast and skin biopsies from systemic sclerosis patients were used. Myofibroblast differentiation, gene expression and cytokine secretion were measured following LPA and/or SAR100842 treatment. Pharmacolgical effect of SAR100842 was assessed in the tight skin 1 (Tsk1) mouse model. KEY RESULTS: SAR100842 is equipotent against various LPA isoforms. Dermal fibroblasts and skin biopsies from patients with systemic sclerosis expressed high levels of LPA1 receptor. The LPA functional response (Ca2+ ) in systemic sclerosis dermal fibroblasts was fully antagonized with SAR100842. LPA induced myofibroblast differentiation in systemic sclerosis dermal and idiopathic pulmonary fibrosis lung fibroblasts and the secretion of inflammatory markers and activated Wnt markers. Results from systemic sclerosis dermal fibroblasts mirror those obtained in a mouse Tsk1 model of skin fibrosis. Using a therapeutic protocol, SAR100842 consistently reversed dermal thickening, inhibited myofibroblast differentiation and reduced skin collagen content. Inflammatory and Wnt pathway markers were also inhibited by SAR100842 in the skin of Tsk1 mice. CONCLUSION AND IMPLICATIONS: The effects of SAR100842 on LPA-induced inflammation and on mechanisms linked to fibrosis like myofibroblast differentiation and Wnt pathway activation indicate that LPA1 receptor activation plays a key role in skin fibrosis. Our results support the therapeutic potential of LPA1 receptor antagonists in systemic sclerosis.

Healthy Donors Exhibit a CD4 T Cell Repertoire Specific to the Immunogenic Human Hormone H2-Relaxin before Injection.

H2-relaxin (RLN2) is a two-chain peptide hormone structurally related to insulin with a therapeutic potential in multiple indications. However, multiple injections of human RLN2 induced anti-RLN2 Abs in patients, hampering its clinical development. As T cell activation is required to produce Abs, we wondered whether T cells specific for RLN2 might be already present in the human blood before any injection. We therefore quantified the RLN2-specific T cell repertoire using PBMCs collected from healthy donors. CD4 T cells were stimulated in multiple replicates by weekly rounds of stimulation by dendritic cells loaded with RLN2, and their specificity was assessed by IFN-γ ELISPOT. The number of specific T cell lines was used to estimate the frequency of circulating T cells. In vitro T cell response was demonstrated in 18 of the 23 healthy donors, leading to the generation of 70 independent RLN2-specific T cell lines. The mean frequency of RLN2-specific CD4 T cells was similar to that of T cells specific for known immunogenic therapeutic proteins. Using overlapping peptides, we identified multiple T cell epitopes hosted in the N-terminal parts of the α- and ß-chains and common to multiple donors, in agreement with their capacity to bind to multiple HLA-DR molecules. Our results provide important clues to the immunogenicity of RLN2 and highlight the weak central immune tolerance induced against this self-hormone.

Lysophosphatidic Acid Receptor 1 Antagonist SAR100842 for Patients With Diffuse Cutaneous Systemic Sclerosis: A Double-Blind, Randomized, Eight-Week Placebo-Controlled Study Followed by a Sixteen-Week Open-Label Extension Study.

OBJECTIVE: Preclinical studies suggest a role for lysophosphatidic acid (LPA) in the pathogenesis of systemic sclerosis (SSc). We undertook this study to assess SAR100842, a potent selective oral antagonist of the LPA1 receptor, for safety, biomarkers, and clinical efficacy in patients with diffuse cutaneous SSc (dcSSc). METHODS: An 8-week double-blind, randomized, placebo-controlled study followed by a 16-week open-label extension with SAR100842 was performed in patients with early dcSSc who had a baseline modified Rodnan skin thickness score (MRSS) of at least 15. The primary end point was safety during the double-blind phase of the trial. Exploratory end points included the identification of an LPA-induced gene signature in patients' skin. RESULTS: Seventeen of 32 patients were randomly assigned to receive placebo and 15 to receive SAR100842; 30 patients participated in the open-label extension study. The most frequent adverse events reported for SAR100842 during the blinded phase were headache, diarrhea, nausea, and falling, and the safety profile was acceptable during the open-label extension. At week 8, the reduction in MRSS was numerically greater in the SAR100842 group than in the placebo group (mean ± SD change -3.57 ± 4.18 versus -2.76 ± 4.85; treatment effect -1.2 [95% confidence interval -4.37, 2.02]; P = 0.46). A greater reduction of LPA-related genes was observed in skin samples from the SAR100842 group at week 8, indicating LPA1 target engagement. CONCLUSION: SAR100842, a selective orally available LPA1 receptor antagonist, was well tolerated in patients with dcSSc. The MRSS improved during the study although the difference was not significant, and additional gene signature analysis suggested target engagement. These results need to be confirmed in a larger controlled trial.

Limited fibrosis accompanies triple-negative breast cancer metastasis in multiple model systems and is not a preventive target.

The lysophosphatidic acid receptor 1 (LPAR1) is mechanistically implicated in both tumor metastasis and tissue fibrosis. Previously, metastasis was increased when fulminant fibrosis was first induced in mice, suggesting a direct connection between these processes. The current report examined the extent of metastasis-induced fibrosis in breast cancer model systems, and tested the metastasis preventive efficacy and fibrosis attenuation of antagonists for LPAR1 and Idiopathic Pulmonary Fibrosis (IPF) in breast and ovarian cancer models. Staining analysis demonstrated only focal, low-moderate levels of fibrosis in lungs from eleven metastasis model systems. Two orally available LPAR1 antagonists, SAR100842 and EPGN9878, significantly inhibited breast cancer motility to LPA in vitro. Both compounds were negative for metastasis prevention and failed to reduce fibrosis in the experimental MDA-MB-231T and spontaneous murine 4T1 in vivo breast cancer metastasis models. SAR100842 demonstrated only occasional reductions in invasive metastases in the SKOV3 and OVCAR5 ovarian cancer experimental metastasis models. Two approved drugs for IPF, nintedanib and pirfenidone, were investigated. Both were ineffective at preventing MDA-MB-231T metastasis, with no attenuation of fibrosis. In summary, metastasis-induced fibrosis is only a minor component of metastasis in untreated progressive breast cancer. LPAR1 antagonists, despite in vitro evidence of specificity and efficacy, were ineffective in vivo as oral agents, as were approved IPF drugs. The data argue against LPAR1 and fibrosis as monotherapy targets for metastasis prevention in triple-negative breast cancer and ovarian cancer.

PCSK9 Modulates the Secretion But Not the Cellular Uptake of Lipoprotein(a) Ex Vivo: An Effect Blunted by Alirocumab.

To elucidate how the proprotein convertase subtilisin kexin type 9 (PCSK9) inhibitor alirocumab modulates lipoprotein(a) [Lp(a)] plasma levels, the authors performed a series of Lp(a) uptake studies in primary human hepatocytes and dermal fibroblasts and measured Lp(a) secretion from human hepatocytes. They found that Lp(a) cellular uptake occurred in a low-density lipoprotein receptor-independent manner. Neither PCSK9 nor alirocumab altered Lp(a) internalization. By contrast, the secretion of apolipoprotein (a) from human hepatocytes was sharply increased by PCSK9, an effect that was reversed by alirocumab. They propose that PCSK9 does not significantly modulate Lp(a) catabolism, but rather enhances the secretion of Lp(a) from liver cells.