Marina Protopopova

Pharmacodynamics and pharmacokinetics of SQ109, a new diamine‐based antitubercular drug

1 SQ109 is a novel [1,2]‐diamine‐based ethambutol (EMB) analog developed from high‐throughput combinatorial screening. The present study aimed at characterizing its pharmacodynamics and pharmacokinetics. 2 The antimicrobial activity of SQ109 was confirmed in vitro (Mycobacterium tuberculosis‐infected murine macrophages) and in vivo (M. tuberculosis‐infected C57BL/6 mice) and compared to isoniazid (INH) and EMB. SQ109 showed potency and efficacy in inhibiting intracellular M. tuberculosis that was similar to INH, but superior to EMB. In vivo oral administration of SQ109 (0.1–25 mg kg−1 day−1) to the mice for 28 days resulted in dose‐dependent reductions of mycobacterial load in both spleen and lung comparable to that of EMB administered at 100 mg kg−1 day−1, but was less potent than INH at 25 mg kg−1 day−1. Monitoring of SQ109 levels in mouse tissues on days 1, 14 and 28 following 28‐day oral administration (10 mg kg−1 day−1) revealed that lungs and spleen contained the highest concentration of SQ109, at least 10 times above its MIC. 3 Pharmacokinetic profiles of SQ109 in mice following a single administration showed its Cmax as 1038 (intravenous (i.v.)) and 135 ng ml−1 (p.o.), with an oral Tmax of 0.31 h. The elimination t1/2 of SQ109 was 3.5 (i.v.) and 5.2 h (p.o.). The oral bioavailability was 4%. However, SQ109 displayed a large volume of distribution into various tissues. The highest concentration of SQ109 was present in lung (>MIC), which was at least 120‐fold (p.o.) and 180‐fold (i.v.) higher than that in plasma. The next ranked tissues were spleen and kidney. SQ109 levels in most tissues after a single administration were significantly higher than that in blood. High tissue concentrations of SQ109 persisted for the observation period (10 h). 4 This study demonstrated that SQ109 displays promising in vitro and in vivo antitubercular activity with favorable targeted tissue distribution properties.

Drug Therapy of Experimental Tuberculosis (TB): Improved Outcome by Combining SQ109, a New Diamine Antibiotic, with Existing TB Drugs

ABSTRACT Substitution of the new diamine antibiotic SQ109 for ethambutol in a mouse model of chronic tuberculosis (TB) improved efficacy of combination drug therapy with first-line TB drugs rifampin and isoniazid, with or without pyrazinamide: at 8 weeks, lung bacteria were 1.5 log10 lower in SQ109-containing regimens.

Activity of SQ641, a Capuramycin Analog, in a Murine Model of Tuberculosis

ABSTRACT New delivery vehicles and routes of delivery were developed for the capuramycin analogue SQ641. While this compound has remarkable in vitro potency against Mycobacterium tuberculosis, it has low solubility in water and poor intracellular activity. We demonstrate here that SQ641 dissolved in the water-soluble vitamin E analogue α-tocopheryl polyethylene glycol 1000 succinate (TPGS) or incorporated into TPGS-micelles has significant activity in a mouse model of tuberculosis.

In Search of New Cures for Tuberculosis

The last 10 years have seen resurgent industry activity in discovery and development of new drugs for the treatment of tuberculosis (TB), a growing widespread and devastating (more than 2 million deaths annually) bacterial infection that is of increasing concern in developing and developed nations alike. This review describes drugs currently being evaluated in the clinic for treatment of uncomplicated and drug resistant pulmonary TB, and updates the literature on 5 new drugs that entered clinical trials in the last 4 years.

Identification of SQ609 as a lead compound from a library of dipiperidines

We recently reported that compounds created around a dipiperidine scaffold demonstrated activity against Mycobacterium tuberculosis (Mtb) (Bogatcheva, E.; Hanrahan, C.; Chen, P.; Gearhart, J.; Sacksteder, K.; Einck, L.; Nacy, C.; Protopopova, M. Bioorg. Med. Chem. Lett.2010, 20, 201). To optimize the dipiperidine compound series and to select a lead compound to advance into preclinical studies, we evaluated the structure-activity relationship (SAR) of our proprietary libraries. The (piperidin-4-ylmethyl)piperidine scaffold was an essential structural element required for antibacterial activity. Based on SAR, we synthesized a focused library of 313 new dipiperidines to delineate additional structural features responsible for antitubercular activity. Thirty new active compounds with MIC 10-20 μg/ml on Mtb were identified, but none was better than the original hits of this series, SQ609, SQ614, and SQ615. In Mtb-infected macrophages in vitro, SQ609 and SQ614 inhibited more than 90% of intracellular bacterial growth at 4 μg/ml; SQ615 was toxic to these cells. In mice infected with Mtb, weight loss was completely prevented by SQ609, but not SQ614, and SQ609 had a prolonged therapeutic effect, extended by 10-15 days, after cessation of therapy. Based on in vitro and in vivo antitubercular activity, SQ609 was identified as the best-in-class dipiperidine compound in the series.

Chemical modification of capuramycins to enhance antibacterial activity

OBJECTIVES To extend capuramycin spectrum of activity beyond mycobacteria and improve intracellular drug activity. METHODS Three capuramycin analogues (SQ997, SQ922 and SQ641) were conjugated with different natural and unnatural amino acids or decanoic acid (DEC) through an ester bond at one or more available hydroxyl groups. In vitro activity of the modified compounds was determined against Mycobacterium spp. and representative Gram-positive and Gram-negative bacteria. Intracellular activity was evaluated in J774A.1 mouse macrophages infected with Mycobacterium tuberculosis (H37Rv). RESULTS Acylation of SQ997 and SQ641 with amino undecanoic acid (AUA) improved in vitro activity against most of the bacteria tested. Conjugation of SQ922 with DEC, but not AUA, improved its activity against Gram-positive bacteria. In the presence of efflux pump inhibitor phenylalanine arginine β-naphthyl amide, MICs of SQ997-AUA, SQ641-AUA and SQ922-DEC compounds improved even further against drug-susceptible and drug-resistant Staphylococcus aureus. In Gram-negative bacteria, EDTA-mediated permeabilization caused 4- to 16-fold enhancement of the activity of AUA-conjugated SQ997, SQ922 and SQ641. Conjugation of all three capuramycin analogues with AUA improved intracellular killing of H37Rv in murine macrophages. CONCLUSIONS Conjugation of capuramycin analogues with AUA or DEC enhanced in vitro activity, extended the spectrum of activity in Gram-positive bacteria and increased intracellular activity against H37Rv.

Discovery of dipiperidines as new antitubercular agents

As part of our ongoing research effort to develop new therapeutics for treatment of tuberculosis (TB), we synthesized a combinatorial library of 10,358 compounds on solid support using a pool-and-split technique and tested the resulting compounds for activity against Mycobacteriumtuberculosis. Structure-activity relationship (SAR) evaluation identified new compounds with antitubercular activity, including a novel hit series that is structurally unrelated to any existing antitubercular drugs, dipiperidines. Dipiperidine representatives exhibited MIC values as low as 7.8microM, the ability to induce promoter Rv0341 activated in response to cell wall biosynthesis inhibition, relatively low nonspecific cellular toxicity in the range of 30-162microM, and logP values less than 4.