Venkata Ramana Doppalapudi

Specifically Targeting Angiopoietin-2 Inhibits Angiogenesis, Tie2-Expressing Monocyte Infiltration, and Tumor Growth

Purpose: Angiopoietin-1 (Ang1) plays a key role in maintaining stable vasculature, whereas in a tumor Ang2 antagonizes Ang1s function and promotes the initiation of the angiogenic switch. Specifically targeting Ang2 is a promising anticancer strategy. Here we describe the development and characterization of a new class of biotherapeutics referred to as CovX-Bodies, which are created by chemical fusion of a peptide and a carrier antibody scaffold. Experimental Design: Various linker tethering sites on peptides were examined for their effect on CovX-Body in vitro potency and pharmacokinetics. Ang2 CovX-Bodies with low nmol/L IC50s and significantly improved pharmacokinetics were tested in tumor xenograft studies alone or in combination with standard of care agents. Tumor samples were analyzed for target engagement, via Ang2 protein level, CD31-positive tumor vasculature, and Tie2 expressing monocyte penetration. Results: Bivalent Ang2 CovX-Bodies selectively block the Ang2–Tie2 interaction (IC50 < 1 nmol/L) with dramatically improved pharmacokinetics (T½ > 100 hours). Using a staged Colo-205 xenograft model, significant tumor growth inhibition (TGI) was observed (40%–63%, P < 0.01). Ang2 protein levels were reduced by approximately 50% inside tumors (P < 0.01), whereas tumor microvessel density (P < 0.01) and intratumor proangiogenic Tie2+CD11b+ cells (P < 0.05) were significantly reduced. When combined with sunitinib, sorafenib, bevacizumab, irinotecan, or docetaxel, Ang2 CovX-Bodies produced even greater efficacy (∼80% TGI, P < 0.01). Conclusion: CovX-Bodies provide an elegant solution to overcome the pharmacokinetic–pharmacodynamic problems of peptides. Long-acting Ang2 specific CovX-Bodies will be useful as single agents and in combination with standard-of-care agents. Clin Cancer Res; 17(5); 1001–11. ©2011 AACR.

Chemical generation of bispecific antibodies

Bispecific antibodies (BsAbs) are regarded as promising therapeutic agents due to their ability to simultaneously bind two different antigens. Several bispecific modalities have been developed, but their utility is limited due to problems with stability and manufacturing complexity. Here we report a versatile technology, based on a scaffold antibody and pharmacophore peptide heterodimers, that enables rapid generation and chemical optimization of bispecific antibodies, which are termed bispecific CovX-Bodies. Two different peptides are joined together using a branched azetidinone linker and fused to the scaffold antibody under mild conditions in a site-specific manner. Whereas the pharmacophores are responsible for functional activities, the antibody scaffold imparts long half-life and Ig-like distribution. The pharmacophores can be chemically optimized or replaced with other pharmacophores to generate optimized or unique bispecific antibodies. As a prototype, we developed a bispecific antibody that binds both vascular endothelial growth factor (VEGF) and angiopoietin-2 (Ang2) simultaneously, inhibits their function, shows efficacy in tumor xenograft studies, and greatly augments the antitumor effects of standard chemotherapy. This unique antiangiogenic bispecific antibody is in phase-1 clinical trials.

NB2001, a Novel Antibacterial Agent with Broad-Spectrum Activity and Enhanced Potency against β-Lactamase-Producing Strains

ABSTRACT Enzyme-catalyzed therapeutic activation (ECTA) is a novel prodrug strategy to overcome drug resistance resulting from enzyme overexpression. β-Lactamase overexpression is a common mechanism of bacterial resistance to β-lactam antibiotics. We present here the results for one of the β-lactamase ECTA compounds, NB2001, which consists of the antibacterial agent triclosan in a prodrug form with a cephalosporin scaffold. Unlike conventional β-lactam antibiotics, where hydrolysis of the β-lactam ring inactivates the antibiotic, hydrolysis of NB2001 by β-lactamase releases triclosan. Evidence supporting the proposed mechanism is as follows. (i) NB2001 is a substrate for TEM-1 β-lactamase, forming triclosan with a second-order rate constant (kcat/Km) of greater than 77,000 M−1 s−1. (ii) Triclosan is detected in NB2001-treated, β-lactamase-producing Escherichia coli but not in E. coli that does not express β-lactamase. (iii) NB2001 activity against β-lactamase-producing E. coli is decreased in the presence of the β-lactamase inhibitor clavulanic acid. NB2001 was similar to or more potent than reference antibiotics against clinical isolates of Staphylococcus aureus (including MRSA), Staphylococcus epidermidis, Streptococcus pneumoniae, vancomycin-resistant Enterococcus faecalis, Moraxella catarrhalis and Haemophilus influenzae. NB2001 is also active against Klebsiella pneumoniae, Enterobacter aerogenes, and Enterobacter cloacae. The results indicate that NB2001 is a potent, broad-spectrum antibacterial agent and demonstrate the potential of ECTA in overcoming β-lactamase-mediated resistance.

The synthesis and evaluation of 3-substituted-7-(alkylidene)cephalosporin sulfones as β-lactamase inhibitors

A series of 3-substituted-7-(alkylidene)cephaloporin sulfones were prepared and evaluated as inhibitors of representative class A and class C serine beta-lactamase. Appropriate substituents resulted in a 1000-fold improvement in the inhibition of the class A enzymes and a simultaneous 20-fold improvement in the inhibition of class C. These new compounds have achieved the goal of creating broad scale inhibitors in the cephalosporin series.

Penicillin Sulfone Inhibitors of Class D β-Lactamases

ABSTRACT OXA β-lactamases are largely responsible for β-lactam resistance in Acinetobacter spp. and Pseudomonas aeruginosa, two of the most difficult-to-treat nosocomial pathogens. In general, the β-lactamase inhibitors used in clinical practice (clavulanic acid, sulbactam, and tazobactam) demonstrate poor activity against class D β-lactamases. To overcome this challenge, we explored the abilities of β-lactamase inhibitors of the C-2- and C-3-substituted penicillin and cephalosporin sulfone families against OXA-1, extended-spectrum (OXA-10, OXA-14, and OXA-17), and carbapenemase-type (OXA-24/40) class D β-lactamases. Three C-2-substituted penicillin sulfone compounds (JDB/LN-1-255, JDB/LN-III-26, and JDB/ASR-II-292) showed low Ki values for the OXA-1 β-lactamase (0.70 ± 0.14 → 1.60 ± 0.30 μM) and demonstrated significant Ki improvements compared to the C-3-substituted cephalosporin sulfone (JDB/DVR-II-214), tazobactam, and clavulanic acid. The C-2-substituted penicillin sulfones JDB/ASR-II-292 and JDB/LN-1-255 also demonstrated low Kis for the OXA-10, -14, -17, and -24/40 β-lactamases (0.20 ± 0.04 → 17 ± 4 μM). Furthermore, JDB/LN-1-255 displayed stoichiometric inactivation of OXA-1 (the turnover number, i.e., the partitioning of the initial enzyme inhibitor complex between hydrolysis and enzyme inactivation [tn] = 0) and tns ranging from 5 to 8 for the other OXA enzymes. Using mass spectroscopy to study the intermediates in the inactivation pathway, we determined that JDB/LN-1-255 inhibited OXA β-lactamases by forming covalent adducts that do not fragment. On the basis of the substrate and inhibitor kinetics of OXA-1, we constructed a model showing that the C-3 carboxylate of JDB/LN-1-255 interacts with Ser115 and Thr213, the R-2 group at C-2 fits between the space created by the long B9 and B10 β strands, and stabilizing hydrophobic interactions are formed between the pyridyl ring of JDB/LN-1-255 and Val116 and Leu161. By exploiting conserved structural and mechanistic features, JDB/LN-1-255 is a promising lead compound in the quest for effective inhibitors of OXA-type β-lactamases.

Cephalosporin-derived inhibitors of β-lactamase. Part 4: The C3 substituent

New C3-substituted β-lactamase inhibitors were prepared and evaluated against representative class A and class C enzymes. It was possible to improve simultaneous inhibitory activity of both classes of serine hydrolase. Other inhibitors showed high selectivity for either the class C cephalosporinases or the class A penicillinases. This represents the first time that cephalosporin-derived inhibitors have demonstrated selectivity for the class A β-lactamases.

Evolution of potent and stable placental-growth-factor-1-targeting CovX-bodies from phage display peptide discovery.

Novel phage-derived peptides are the first reported molecules specifically targeting human placental growth factor 1 (PlGF-1). Phage data enabled peptide modifications that decreased IC(50) values in PlGF-1/VEGFR-1 competition ELISA from 100 to 1 μM. Peptides exhibiting enhanced potency were bioconjugated to the CovX antibody scaffold 1 (CVX-2000), generating bivalent CovX-Bodies with 2 nM K(D) against PlGF-1. In vitro and in vivo peptide cleavage mapping studies enabled the identification of proteolytic hotspots that were subsequently chemically modified. These changes decreased IC(50) to 0.4 nM and increased compound stability from 5% remaining at 6 h after injection to 35% remaining at 24 h with a β phase half-life of 75 h in mice. In cynomolgus monkey, a 78 h β half-life was observed for lead compound 2. The pharmacological properties of 2 are currently being explored.

Stille coupling approaches to the stereospecific synthesis of 7-[(E)-alkylidene]cephalosporins

Stille coupling methodology is used to stereospecifically synthesize 7-[(E)-alkylidene]cephalosporins, potential enzyme inhibitors which are unavailable via other synthetic methodology. Two procedures are described, utilizing either a stannylalkylidene cephem which is then coupled with an organohalide, or a haloalkylidene cephem which is coupled with an organostannane.

Catalytic Approaches to the Synthesis of β-Lactamase Inhibitors

Abstract Catalytic couplings were utilized to stereospecifically synthesize several 7 E - and 7 Z -alkylidenecephalosporins. Members of this class are known inhibitors of β-lactamase. Zinc/NH 4 Cl reduction of dibromide 14 stereospecifically produced E -monobromide, 15 . In contrast, treatment of 14 with isopropylmagnesium bromide, followed by mild acid, stereospecifically produced Z -monobromide 27 . These reactions involve stable, intermediate α-(metalloalkylidene)-β-lactams. Monobromides 15 and 27 were stereospecifically coupled to organostannanes, or were converted to the corresponding organostannanes, 22 and 32 , which coupled with organohalides.