Acid-Labile Thermoresponsive Copolymers That Combine Fast pH-Triggered Hydrolysis and High Stability under Neutral Conditions.

Biodegradable polymeric materials are intensively used in biomedical applications. Of particular interest for drug-delivery applications are polymers that are stable at pH 7.4, that is, in the blood stream, but rapidly hydrolyze under acidic conditions, such as those encountered in the endo/lysosome or the tumor microenvironment. However, an increase in the acidic-degradation rate of acid-labile groups goes hand in hand with higher instability of the polymer at pH 7.4 or during storage, thus posing an intrinsic limitation on fast degradation under acidic conditions. Herein, we report that a combination of acid-labile dimethyldioxolane side chains and hydroxyethyl side chains leads to acid-degradable thermoresponsive polymers that are quickly hydrolyzed under slightly acidic conditions but stable at pH 7.4 or during storage. We ascribe these properties to high hydration of the hydroxy-containing collapsed polymer globules in conjunction with autocatalytic acceleration of the hydrolysis reactions by the hydroxy groups.

The anticancer effect of phospho-tyrosol-indomethacin (MPI-621), a novel phosphoderivative of indomethacin: in vitro and in vivo studies.

We have synthesized a novel derivative of indomethacin, phospho-tyrosol-indomethacin (PTI; MPI-621), and evaluated its anticancer efficacy in vitro and in vivo. PTI inhibited the growth of human colon, breast and lung cancer cell lines 6-30-fold more potently than indomethacin. In vivo, in contrast to indomethacin that was unable to inhibit colon cancer xenograft growth, PTI inhibited the growth of colon (69% at 10mg/kg/day, P < 0.01) and lung (91% at 15mg/kg/day, P < 0.01) subcutaneous cancer xenografts in immunodeficient mice, suppressing cell proliferation by 33% and inducing apoptosis by 75% (P < 0.05, for both). Regarding its pharmacokinetics in mice, after a single intraperitoneal injection of PTI, its plasma levels reached the maximum concentration (Cmax = 46 µM) at 2h (Tmax) and became undetectable at 4h. Indomethacin is the major metabolite of PTI, with plasma Cmax = 378 µM and Tmax = 2.5h; it became undetectable 24h postadministration. The cellular uptake of PTI (50-200 µM) at 6h was about 200-fold greater than that of indomethacin. Regarding its safety, PTI had no significant genotoxicity, showed less gastrointestinal toxicity than indomethacin and presented no cardiac toxicity. Mechanistically, PTI suppressed prostaglandin E2 production in A549 human lung cancer cells and strongly inhibited nuclear factor-κB activation in A549 xenografts. These findings indicate that PTI merits further evaluation as an anticancer agent.

Carboxylesterases 1 and 2 hydrolyze phospho-nonsteroidal anti-inflammatory drugs: relevance to their pharmacological activity.

Phospho-nonsteroidal anti-inflammatory drugs (phospho-NSAIDs) are novel NSAID derivatives with improved anticancer activity and reduced side effects in preclinical models. Here, we studied the metabolism of phospho-NSAIDs by carboxylesterases and assessed the impact of carboxylesterases on the anticancer activity of phospho-NSAIDs in vitro and in vivo. The expression of human liver carboxylesterase (CES1) and intestinal carboxylesterase (CES2) in human embryonic kidney 293 cells resulted in the rapid intracellular hydrolysis of phospho-NSAIDs. Kinetic analysis revealed that CES1 is more active in the hydrolysis of phospho-sulindac, phospho-ibuprofen, phospho-naproxen, phospho-indomethacin, and phospho-tyrosol-indomethacin that possessed a bulky acyl moiety, whereas the phospho-aspirins are preferentially hydrolyzed by CES2. Carboxylesterase expression leads to a significant attenuation of the in vitro cytotoxicity of phospho-NSAIDs, suggesting that the integrity of the drug is critical for anticancer activity. Benzil and bis-p-nitrophenyl phosphate (BNPP), two carboxylesterase inhibitors, abrogated the effect of carboxylesterases and resensitized carboxylesterase-expressing cells to the potent cytotoxic effects of phospho-NSAIDs. In mice, coadministration of phospho-sulindac and BNPP partially protected the former from esterase-mediated hydrolysis, and this combination more effectively inhibited the growth of AGS human gastric xenografts in nude mice (57%) compared with phospho-sulindac alone (28%) (p = 0.037). Our results show that carboxylesterase mediates that metabolic inactivation of phospho-NSAIDs, and the inhibition of carboxylesterases improves the efficacy of phospho-NSAIDs in vitro and in vivo.

Comparative in vitro metabolism of phospho-tyrosol-indomethacin by mice, rats and humans.

Phospho-tyrosol-indomethacin (PTI; MPI 621), a novel anti-cancer agent, is more potent and safer than conventional indomethacin. Here, we show that PTI was extensively metabolized in vitro and in vivo. PTI was rapidly hydrolyzed by carboxylesterases to generate indomethacin as its major metabolite in the liver microsomes and rats. PTI additionally undergoes cytochromes P450 (CYP)-mediated hydroxylation at its tyrosol moiety and O-demethylation at its indomethacin moiety. Of the five major human CYPs, CYP3A4 and CYP2D6 catalyze the hydroxylation and O-demethylation reactions of PTI, respectively; whereas CYP1A2, 2C9 and 2C19 are inactive towards PTI. In contrast to PTI, indomethacin is primarily O-demethylated by CYP2C9, which prefers acidic substrates. The hydrolyzed and O-demethylated metabolites of PTI are further glucuronidated and sulfated, facilitating drug elimination and detoxification. We observed substantial inter-species differences in the metabolic rates of PTI. Among the liver microsomes from various species, PTI was the most rapidly hydrolyzed, hydroxylated and O-demethylated in mouse, human and rat liver microsomes, respectively. These results reflect the differential expression patterns of carboxylesterase and CYP isoforms among these species. Of the human microsomes from various tissues, PTI underwent more rapid carboxylesterase- and CYP-catalyzed reactions in liver and intestine microsomes than in kidney and lung microsomes. Together, our results establish the metabolic pathways of PTI, reveal significant inter-species differences in its metabolism, and provide insights into the underlying biochemical mechanisms.

MC-12, an annexin A1-based peptide, is effective in the treatment of experimental colitis.

Annexin A1 (ANXA1) inhibits NF-κB, a key regulator of inflammation, the common pathophysiological mechanism of inflammatory bowel diseases (IBD). MC-12, an ANXA1-based tripeptide, suppresses NF-κB activation. Here, we determined the efficacy of MC-12 in the control of IBD. Mice with colitis induced by dextran sodium sulfate (DSS) or 2,4,6-trinitro benzene sulfonic acid (TNBS) were treated with various doses of MC-12 administered intraperitoneally, orally or intrarectally. We determined colon length and the histological score of colitis, and assayed: in colon tissue the levels of TNF-α, IFN-γ, IL-1ß, IL-6 and IL-10 by RT-PCR; prostaglandin E(2) (PGE(2)), cytoplasmic phospholipase A(2) (cPLA(2)) and myeloperoxidase by immunoassay; and COX-2 and NF- κB by immunohistochemistry; and in serum the levels of various cytokines by immunoassay. In both models MC-12: reversed dose-dependently colonic inflammation; inhibited by up to 47% myeloperoxidase activity; had a minimal effect on cytoplasmic phospholipase A(2); reduced significantly the induced levels of TNF-α, IFN-γ, IL-1ß, IL-6 and IL-10, returning them to baseline. DSS and TNBS markedly activated NF-κB in colonic epithelial cells and MC-12 decreased this effect by 85.8% and 72.5%, respectively. MC-12 had a similar effect in cultured NCM460 normal colon epithelial cells. Finally, MC-12 suppressed the induction of COX-2 expression, the level of PGE(2) in the colon and PGE(2) metabolite in serum. In conclusion, MC-12, representing a novel class of short peptide inhibitors of NF-κB, has a strong effect against colitis in two preclinical models recapitulating features of human IBD. Its mechanism of action is complex and includes pronounced inhibition of NF-κB. MC-12 merits further development as an agent for the control of IBD.