Hemoglobin-Based Oxygen Carrier Microparticles: Synthesis, Properties, and In Vitro and In Vivo Investigations

Bovine hemoglobin microparticles (Hb-MPs) as suitable oxygen carriers are fabricated easily by three key steps: coprecipitation of Hb and CaCO₃ to make Hb-CaCO₃-microparticles (Hb-CaCO₃-MPs), cross-linking by glutaraldehyde (GA) to polymerize the Hb and dissolution of CaCO₃ template to obtain pure Hb-MPs. The Hb entrapment efficiency ranged from 8 to 50% corresponding to a hemoglobin quantity per Hb-MP of at least one-third of that in one erythrocyte. The Hb-MPs are spherical, with an average diameter of 3.2 μm and high oxygen affinity. The methemoglobin level was increased after preparation, but can be reduced to less than 7% with ascorbic acid. Phagocytosis assays showed low immunogenicity of Hb-MPs if the particles were cross-linked with low concentration of GA and treated with sodium borohydride. Magnetite-loaded Hb-MPs circulated up to 4 days after intravenous application

Development of Selective CBP/P300 Benzoxazepine Bromodomain Inhibitors

CBP (CREB (cAMP responsive element binding protein) binding protein (CREBBP)) and P300 (adenovirus E1A-associated 300 kDa protein) are two closely related histone acetyltransferases (HATs) that play a key role in the regulation of gene transcription. Both proteins contain a bromodomain flanking the HAT catalytic domain that is important for the targeting of CBP/P300 to chromatin and which offeres an opportunity for the development of protein–protein interaction inhibitors. Here we present the development of CBP/P300 bromodomain inhibitors with 2,3,4,5-tetrahydro-1,4-benzoxazepine backbone, an <i>N</i>-acetyl-lysine mimetic scaffold that led to the recent development of the chemical probe I-CBP112. We present comprehensive SAR of this inhibitor class as well as demonstration of cellular on target activity of the most potent and selective inhibitor TPOP146, which showed 134 nM affinity for CBP with excellent selectivity over other bromodomains

Development of Selective CBP/P300 Benzoxazepine Bromodomain Inhibitors

CBP (CREB (cAMP responsive element binding protein) binding protein (CREBBP)) and P300 (adenovirus E1A-associated 300 kDa protein) are two closely related histone acetyltransferases (HATs) that play a key role in the regulation of gene transcription. Both proteins contain a bromodomain flanking the HAT catalytic domain that is important for the targeting of CBP/P300 to chromatin and which offeres an opportunity for the development of protein–protein interaction inhibitors. Here we present the development of CBP/P300 bromodomain inhibitors with 2,3,4,5-tetrahydro-1,4-benzoxazepine backbone, an <i>N</i>-acetyl-lysine mimetic scaffold that led to the recent development of the chemical probe I-CBP112. We present comprehensive SAR of this inhibitor class as well as demonstration of cellular on target activity of the most potent and selective inhibitor TPOP146, which showed 134 nM affinity for CBP with excellent selectivity over other bromodomains

Development and Characterization of Type I, Type II, and Type III LIM-Kinase Chemical Probes

LIMKs are important regulators of actin and microtubule dynamics, and they play essential roles in many cellular processes. Deregulation of LIMKs has been linked to the development of diverse diseases, including cancers and cognitive disabilities, but well-characterized inhibitors known as chemical probes are still lacking. Here, we report the characterization of three highly selective LIMK1/2 inhibitors covering all canonical binding modes (type I/II/III) and the structure-based design of the type II/III inhibitors. Characterization of these chemical probes revealed a low nanomolar affinity for LIMK1/2, and all inhibitors 1 (LIMKi3; type I), 48 (TH470; type II), and 15 (TH257; type III) showed excellent selectivity in a comprehensive scanMAX kinase selectivity panel. Phosphoproteomics revealed remarkable differences between type I and type II inhibitors compared with the allosteric inhibitor 15. In phenotypic assays such as neurite outgrowth models of fragile X-chromosome, 15 showed promising activity, suggesting the potential application of allosteric LIMK inhibitors treating this orphan disease

Development and Characterization of Type I, Type II, and Type III LIM-Kinase Chemical Probes

LIMKs are important regulators of actin and microtubule dynamics, and they play essential roles in many cellular processes. Deregulation of LIMKs has been linked to the development of diverse diseases, including cancers and cognitive disabilities, but well-characterized inhibitors known as chemical probes are still lacking. Here, we report the characterization of three highly selective LIMK1/2 inhibitors covering all canonical binding modes (type I/II/III) and the structure-based design of the type II/III inhibitors. Characterization of these chemical probes revealed a low nanomolar affinity for LIMK1/2, and all inhibitors 1 (LIMKi3; type I), 48 (TH470; type II), and 15 (TH257; type III) showed excellent selectivity in a comprehensive scanMAX kinase selectivity panel. Phosphoproteomics revealed remarkable differences between type I and type II inhibitors compared with the allosteric inhibitor 15. In phenotypic assays such as neurite outgrowth models of fragile X-chromosome, 15 showed promising activity, suggesting the potential application of allosteric LIMK inhibitors treating this orphan disease

Development, Optimization, and Structure–Activity Relationships of Covalent-Reversible JAK3 Inhibitors Based on a Tricyclic Imidazo[5,4‑<i>d</i>]pyrrolo[2,3‑<i>b</i>]pyridine Scaffold

Janus kinases are major drivers of immune signaling and have been the focus of anti-inflammatory drug discovery for more than a decade. Because of the invariable colocalization of JAK1 and JAK3 at cytokine receptors, the question if selective JAK3 inhibition is sufficient to effectively block downstream signaling has been highly controversial. Recently, we discovered the covalent-reversible JAK3 inhibitor FM-381 (<b>23</b>) featuring high isoform and kinome selectivity. Crystallography revealed that this inhibitor induces an unprecedented binding pocket by interactions of a nitrile substituent with arginine residues in JAK3. Herein, we describe detailed structure–activity relationships necessary for induction of the arginine pocket and the impact of this structural change on potency, isoform selectivity, and efficacy in cellular models. Furthermore, we evaluated the stability of this novel inhibitor class in <i>in vitro</i> metabolic assays and were able to demonstrate an adequate stability of key compound <b>23</b> for <i>in vivo</i> use

Development, Optimization, and Structure–Activity Relationships of Covalent-Reversible JAK3 Inhibitors Based on a Tricyclic Imidazo[5,4‑<i>d</i>]pyrrolo[2,3‑<i>b</i>]pyridine Scaffold

Janus kinases are major drivers of immune signaling and have been the focus of anti-inflammatory drug discovery for more than a decade. Because of the invariable colocalization of JAK1 and JAK3 at cytokine receptors, the question if selective JAK3 inhibition is sufficient to effectively block downstream signaling has been highly controversial. Recently, we discovered the covalent-reversible JAK3 inhibitor FM-381 (<b>23</b>) featuring high isoform and kinome selectivity. Crystallography revealed that this inhibitor induces an unprecedented binding pocket by interactions of a nitrile substituent with arginine residues in JAK3. Herein, we describe detailed structure–activity relationships necessary for induction of the arginine pocket and the impact of this structural change on potency, isoform selectivity, and efficacy in cellular models. Furthermore, we evaluated the stability of this novel inhibitor class in <i>in vitro</i> metabolic assays and were able to demonstrate an adequate stability of key compound <b>23</b> for <i>in vivo</i> use

Discovery of a Chemical Tool Inhibitor Targeting the Bromodomains of TRIM24 and BRPF

TRIM24 is a transcriptional regulator as well as an E3 ubiquitin ligase. It is overexpressed in diverse tumors, and high expression levels have been linked to poor prognosis in breast cancer patients. TRIM24 contains a PHD/bromodomain offering the opportunity to develop protein interaction inhibitors that target this protein interaction module. Here we identified potent acetyl-lysine mimetic benzimidazolones TRIM24 bromodomain inhibitors. The best compound of this series is a selective BRPF1B/TRIM24 dual inhibitor that bound with a <i>K</i>_D of 137 and 222 nM, respectively, but exerted good selectivity over other bromodomains. Cellular activity of the inhibitor was demonstrated using FRAP assays as well as cell viability data

Structure Enabled Design of BAZ2-ICR, A Chemical Probe Targeting the Bromodomains of BAZ2A and BAZ2B

The bromodomain containing proteins BAZ2A/B play essential roles in chromatin remodeling and regulation of noncoding RNAs. We present the structure based discovery of a potent, selective, and cell active inhibitor <b>13</b> (BAZ2-ICR) of the BAZ2A/B bromodomains through rapid optimization of a weakly potent starting point. A key feature of the presented inhibitors is an intramolecular aromatic stacking interaction that efficiently occupies the shallow bromodomain pockets. <b>13</b> represents an excellent chemical probe for functional studies of the BAZ2 bromodomains in vitro and in vivo

[1,2,4]Triazolo[4,3‑<i>a</i>]phthalazines: Inhibitors of Diverse Bromodomains

Bromodomains are gaining increasing interest as drug targets. Commercially sourced and de novo synthesized substituted [1,2,4]­triazolo­[4,3-<i>a</i>]­phthalazines are potent inhibitors of both the BET bromodomains such as BRD4 as well as bromodomains outside the BET family such as BRD9, CECR2, and CREBBP. This new series of compounds is the first example of submicromolar inhibitors of bromodomains outside the BET subfamily. Representative compounds are active in cells exhibiting potent cellular inhibition activity in a FRAP model of CREBBP and chromatin association. The compounds described are valuable starting points for discovery of selective bromodomain inhibitors and inhibitors with mixed bromodomain pharmacology