Design, synthesis and biological characterization of selective LIMK inhibitors.

Inhibitors of LIM kinases are considered of interest for several indications, including elevated intraocular pressure (IOP), cancer, or infection by HIV-1. LX-7101 (Lexicon Pharmaceuticals) was advanced to Phase-I clinical trials as an IOP-lowering agent for treatment of glaucoma. We here discuss the design, synthesis and evaluation of LIMK inhibitors based on a pyrrolopyrimidine scaffold, which represent close analogs of LX-7101. Exploration of structure-activity relationships revealed that many of such compounds, including LX-7101, cause potent inhibition of LIMK1 and LIMK2, and also ROCK2 and PKA. Molecular variations around the various structural elements of LX-7101 were attempted. Substitution on position 6 of the pyrrolopyrimidine scaffold led to the identification of LX-7101 analogs displaying good selectivity versus ROCK, PKA and Akt.

3-[2-(Aminomethyl)-5-[(pyridin-4-yl)carbamoyl]phenyl] benzoates as soft ROCK inhibitors.

Clinical development of ROCK inhibitors has so far been limited by systemic or local ROCK-associated side effects. A soft drug approach, which involves predictable metabolic inactivation of an active compound to a nontoxic metabolite, could represent an attractive way to obtain ROCK inhibitors with improved tolerability. We herein report the design and synthesis of a new series of soft ROCK inhibitors structurally related to the ROCK inhibitor Y-27632. These inhibitors contain carboxylic ester moieties which allow inactivation by esterases. While the parent esters display strong activity in enzymatic (ROCK2) and cellular (MLC phosphorylation) assays, their corresponding carboxylic acid metabolites have negligible functional activity. Compound 32 combined strong efficacy (ROCK2 IC50=2.5 nM) with rapid inactivation in plasma (t1/2 <5'). Compound 32 also demonstrated in vivo efficacy when evaluated as an IOP-lowering agent in ocular normotensive New-Zealand White rabbits, without ocular side effects.

Enhanced Antitumor Efficacy of PhAc-ALGP-Dox, an Enzyme-Activated Doxorubicin Prodrug, in a Panel of THOP1-Expressing Patient-Derived Xenografts of Soft Tissue Sarcoma.

Despite poor response rates and dose-limiting cardiotoxicity, doxorubicin (doxo) remains the standard-of-care for patients with advanced soft tissue sarcoma. We evaluated the efficacy of two tetrapeptidic doxo prodrugs (PhAc-ALGP-Dox or CBR-049 and CBR-050) that are locally activated by enzymes expressed in the tumor environment, in ten sarcoma patient-derived xenografts. Xenograft models were selected based on expression of the main activating enzyme, i.e., thimet oligopeptidase (THOP1). Mice were either randomized to vehicle, doxo, CBR-049 and CBR-050 or control, doxo, aldoxorubicin (aldoxo) and CBR-049. Treatment efficacy was assessed by tumor volume measurement and histological assessment of ex-mouse tumors. CBR-049 showed significant tumor growth delay compared to control in all xenografts investigated and was superior compared to doxo in all but one. At the same time, CBR-049 showed comparable efficacy to aldoxo but the latter was found to have a complex safety profile in mice. CBR-050 demonstrated tumor growth delay compared to control in one xenograft but was not superior to doxo. For both experimental prodrugs, strong immunostaining for THOP1 was found to predict better antitumor efficacy. The prodrugs were well tolerated without any adverse events, even though molar doses were 17-fold higher than those administered and tolerated for doxo.

PhAc-ALGP-Dox, a Novel Anticancer Prodrug with Targeted Activation and Improved Therapeutic Index.

Clinical use of doxorubicin (Dox) is limited by cumulative myelo- and cardiotoxicity. This research focuses on the detailed characterization of PhAc-ALGP-Dox, a targeted tetrapeptide prodrug with a unique dual-step activation mechanism, designed to circumvent Dox-related toxicities and is ready for upcoming clinical investigation. Coupling Dox to a phosphonoacetyl (PhAc)-capped tetrapeptide forms the cell-impermeable, inactive compound, PhAc-ALGP-Dox. After extracellular cleavage by tumor-enriched thimet oligopeptidase-1 (THOP1), a cell-permeable but still biologically inactive dipeptide-conjugate is formed (GP-Dox), which is further processed intracellularly to Dox by fibroblast activation protein-alpha (FAPα) and/or dipeptidyl peptidase-4 (DPP4). In vitro, PhAc-ALGP-Dox is effective in various 2D- and 3D-cancer models, while showing improved safety toward normal epithelium, hematopoietic progenitors, and cardiomyocytes. In vivo, these results translate into a 10-fold higher tolerability and 5-fold greater retention of Dox in the tumor microenvironment compared with the parental drug. PhAc-ALGP-Dox demonstrates 63% to 96% tumor growth inhibition in preclinical models, an 8-fold improvement in efficacy in patient-derived xenograft (PDX) models, and reduced metastatic burden in a murine model of experimental lung metastasis, improving survival by 30%. The current findings highlight the potential clinical benefit of PhAc-ALGP-Dox, a targeted drug-conjugate with broad applicability, favorable tissue biodistribution, significantly improved tolerability, and tumor growth inhibition at primary and metastatic sites in numerous solid tumor models.

Protective role of the inhibitor of apoptosis protein, survivin, in toxin-induced acute renal failure.

Acute renal failure (ARF) is a major worldwide cause of morbidity and mortality, lacking specific targeted, effective therapies. Renal tubular cell apoptosis has been recognized to play a critical role in the pathogenesis of ARF, yet few studies have evaluated whether intervention in apoptotic pathways can ameliorate the deterioration in renal function associated with ARF. Using transgenic mice with diminished levels of the inhibitor of apoptosis protein, survivin, we show that survivin is required to protect the kidney from apoptosis, to suppress renal expression of p53, and to ameliorate renal dysfunction in two models of ARF. Gene delivery of survivin to wild-type mice and mice with 50% levels of survivin, prior to or at the time of induction of ARF, interferes with the deterioration of renal function and preserves the integrity of the kidneys and the renal tubular cells by inhibiting activation of apoptotic pathways in the kidneys and suppressing expression of p53. These results encourage further evaluation of survivin, its active structural domains, and other inhibitors of apoptosis proteins, for preventing and/or treating acute renal failure.

AMA0428, A Potent Rock Inhibitor, Attenuates Early and Late Experimental Diabetic Retinopathy.

PURPOSE: Diabetic retinopathy (DR) is characterized by an early stage of inflammation and vessel leakage, and an advanced vasoproliferative stage. Also, neurodegeneration might play an important role in disease pathogenesis. The aim of this study was to investigate the effect of the Rho kinase (ROCK) inhibitor, AMA0428, on these processes. METHODS: The response to ROCK inhibition by AMA0428 (1 µg) was studied in vivo using the murine model for streptozotocin (STZ)-induced diabetes, focusing on early non-proliferative DR features and the oxygen-induced retinopathy (OIR) model to investigate proliferative DR. Intravitreal (IVT) administration of AMA0428 was compared with murine anti-VEGF-R2 antibody (DC101, 6.2 µg) and placebo (H2O/PEG; 1C8). Outcome was assessed by analyzing leukostasis using fluorescein isothiocyanate coupled concanavalin A (FITC-ConA) and vessel leakage (bovine serum albumin conjugated with fluorescein isothiocyanate; FITC-BSA)/neovascularization and neurodegeneration by immunohistological approaches (hematoxylin and eosin (H&E), terminal deoxynucleotidyl transferase-mediated biotinylated UTP nick end labeling (TUNEL), Brn3a). ELISA and Western blotting were employed to unravel the consequences of ROCK inhibition (1 µM AMA0428) on myosin phosphatase target protein (MYPT)-1 phosphorylation, endothelial nitric oxide synthase (eNOS) phosphorylation, and vascular endothelial growth factor (VEGF) levels in retinas of diabetic mice, on NF-κß activity and ICAM-1 expression in endothelial cells (ECs). RESULTS: In vivo, AMA0428 significantly reduced vessel leakage and neovascularization, respectively, in the STZ and OIR model, comparable to DC101 therapy. Additionally, the ROCK inhibitor decreased neurodegeneration in both models and inhibited leukostasis by 30% (p < 0.05) in the STZ model (p < 0.05), while DC101 had no positive effect on the outcome of these latter processes. ROCK activity was upregulated in the diabetic retina and AMA0428 administration resulted in decreased phospho-MYPT-1, enhanced phospho-eNOS, and reduced VEGF levels. In vitro, AMA0428 interfered with NF-κß activity, thereby inhibiting ICAM-1 expression in ECs. CONCLUSIONS: Targeting ROCK with AMA0428 effectively attenuated outcome in an early DR model (STZ) and a late vasoproliferative retinopathy model (OIR). These findings make AMA0428 a promising candidate with an additional anti-inflammatory and neuroprotective benefit for DR patients, as compared with anti-VEGF treatment.

Rho kinase inhibitor AMA0526 improves surgical outcome in a rabbit model of glaucoma filtration surgery.

PURPOSE: First, to elucidate the effect of Rho kinase inhibitor, AMA0526, on Human Tenon Fibroblast (HTF) proliferation and transdifferentiation to myofibroblasts. Second, the effects of ROCK inhibition on the wound healing process and surgical outcome were investigated in a rabbit model of glaucoma filtration surgery. METHODS: After exposure of HTF to AMA0526 (0.1-25 µM), a water-soluble tetrazolium salt-1 assay and caspase 3/7 activity assay were used to assess its effect on cell proliferation and to elucidate any toxic effects, respectively. Immunohistochemistry of α-smooth muscle actin expression was used to investigate fibroblast-to-myofibroblast differentiation induced by transforming growth factor-beta 1 (TGF-ß1) in the presence or absence of the ROCK inhibitor. The effect of topical treatment was studied in a rabbit model of glaucoma filtration surgery. Treatment outcome was studied by performing intraocular pressure (IOP) measurements and clinical investigation of the bleb area and survival. Immunohistological analysis for inflammation (CD45), angiogenesis (CD31), and collagen I was performed at day 8, 14, and 30 after surgery (n=5/time point). Separate control groups treated with vehicle were used as control. RESULTS: In vitro results showed that AMA0526 dose dependently inhibited proliferation of HTF (P<0.05) without the induction of caspase 3/7 activity. Incubation of HTF with the AMA0526 inhibited TGF-ß1 induced fibroblast-to-myofibroblast differentiation. In the rabbit model, topical treatment significantly improved surgical outcome. Compared to vehicle-treated eyes, AMA0526 resulted in increased bleb area (P<0.0001) and prolonged survival (P=0.0025). IOP remained significantly lower throughout the course of the experiment in the AMA0526 group (P<0.0001). Histological evaluation revealed that blebs treated with the ROCK inhibitor were characterized by reduced inflammation, angiogenesis, and collagen deposition at the site of filtration surgery (P<0.05). CONCLUSIONS: AMA0526 had profound effects on HTF proliferation and myofibroblast transition and improved glaucoma filtration surgery outcome by interfering at different levels of the wound healing process. Therefore, these data indicate that ROCK inhibitors may be considered as more physiological agents which specifically target the wound healing process to improve the outcome of glaucoma surgery.

Inhibition of Rho-Associated Kinase Prevents Pathological Wound Healing and Neovascularization After Corneal Trauma.

PURPOSE: To investigate the effect of AMA0526, a specific inhibitor of rho-associated protein kinase (ROCK), on corneal neovascularization (NV) and scarring in different in vitro and in vivo experimental models. METHODS: The effect of AMA0526 on cell viability, proliferation, and migration of human umbilical vein endothelial cells was determined. Its in vivo topical effect on NV was investigated in the corneal micropocket mouse model (bevacizumab as a control). The vessel length, clock hours, and NV area were measured on photographs. The effect of AMA0526 on pathological wound healing was investigated in the alkali burn mouse model (dexamethasone as a control). Corneas were scored for corneal opacity (CO) and NV after burn injury. Immunohistochemistry was performed to study inflammation, blood vessel density, and collagen III deposition after 7 days. RESULTS: ROCK inhibition significantly inhibited vascular endothelial cell proliferation and migration in vitro in a dose-dependent manner. In the micropocket model, NV was significantly reduced by AMA0526 (37% reduction, P < 0.05) comparable to bevacizumab. CO and NV were reduced after AMA0526, compared with the vehicle (P < 0.05 at all time points from day 3) after chemical burn. AMA0526 resulted in decreased inflammatory cell infiltration (26% reduction, P < 0.01), angiogenesis (47% reduction, P < 0.01), and collagen III deposition (27% reduction, P = 0.009) in the alkali burn model. AMA0526 administration showed results similar to those of dexamethasone with an additional antifibrotic effect. CONCLUSIONS: The ROCK inhibitor, AMA0526, efficiently inhibited angiogenesis in vitro, reduced CO and NV, and controlled the complete process of wound healing in vivo. These results warrant further investigation of the therapeutic potential of AMA0526 for corneal NV and scarring.

The effect of AMA0428, a novel and potent ROCK inhibitor, in a model of neovascular age-related macular degeneration.

PURPOSE: Rho kinase (ROCK) is associated with VEGF-driven angiogenesis, as well as with inflammation and fibrosis. Therefore, the effect of AMA0428, a novel ROCK inhibitor, was studied in these processes, which highly contribute to the pathogenesis of neovascular AMD. METHODS: The effect of AMA0428 (0.5-5.0 µM) on human umbilical vein endothelial cells (HUVECs), human brain microvascular endothelial cells (HBMECs), and human brain microvascular pericytes (HBVPs) was determined using cell viability (WST-1), apoptosis (caspase 3/7), and migration (scratch and under-agarose) assays. The in vivo response was investigated using a laser-induced choroidal neovascularization (CNV) mouse model, in which intravitreal injections of AMA0428, murine anti-VEGF-R2 mAb (DC101), or placebo was given. Outcome was assessed by analysis of inflammation (CD45), angiogenesis (FITC-dextran), vessel leakage (Texas Red-conjugated Dextran and FITC-labeled lectin) and fibrosis (Sirius Red/Collagen I). RESULTS: The AMA0428 dose-dependently reduced proliferation and VEGF-induced migration of HUVEC and HBMEC (P < 0.05). No significant effect was seen on HBVP proliferation; however, migration and pericyte recruitment were enhanced (P < 0.05) by AMA0428 administration. There was no apoptosis induction. The AMA0428 significantly reduced CNV and vessel leakage 2 weeks after laser treatment, comparable to DC101. In addition, AMA0428 inhibited inflammation on day 5 by 42% (P < 0.05) and collagen deposition on day 30 by 43% (P < 0. 05), whereas DC101 had no effect on inflammation nor on fibrosis. CONCLUSIONS: The results suggest that targeting ROCK with AMA0428 not only reduces neoangiogenesis, but also blocks inflammation and fibrosis (contrary to VEGF suppression). These results point to a potential therapeutic benefit of ROCK inhibition in neovascular AMD.

Design, synthesis, and biological evaluation of novel, highly active soft ROCK inhibitors.

ROCK1 and ROCK2 play important roles in numerous cellular functions, including smooth muscle cell contraction, cell proliferation, adhesion, and migration. Consequently, ROCK inhibitors are of interest for treating multiple indications including cardiovascular diseases, inflammatory and autoimmune diseases, lung diseases, and eye diseases. However, systemic inhibition of ROCK is expected to result in significant side effects. Strategies allowing reduced systemic exposure are therefore of interest. In a continuing effort toward identification of ROCK inhibitors, we here report the design, synthesis, and evaluation of novel soft ROCK inhibitors displaying an ester function allowing their rapid inactivation in the systemic circulation. Those compounds display subnanomolar activity against ROCK and strong differences of functional activity between parent compounds and expected metabolites. The binding mode of a representative compound was determined experimentally in a single-crystal X-ray diffraction study. Enzymes responsible for inactivation of these compounds once they enter systemic circulation are also discussed.