Mark Edward Ruppen

PWT-458, a novel pegylated-17-hydroxywortmannin, inhibits phosphatidylinositol 3-kinase signaling and suppresses growth of solid tumors.

Deregulated phosphatidylinositol 3-kinase (PI3K) signaling pathway is widely implicated in tumor growth and resistance to chemotherapy. While a strong rationale exists for pharmacological targeting of PI3K, only a few proof-of-principle in-vivo efficacy studies are currently available. PWT-458, pegylated-17-hydroxywortmannin, is a novel and highly potent inhibitor of PI3K in animal models. Upon in vivo cleavage of its poly(ethyleneglycol) (PEG), PWT-458 releases its active moiety 17-hydroxywortmannin (17-HWT), the most potent inhibitor in its class. Here we show that a single intravenous injection of PWT-458 rapidly inhibited PI3K signaling, as measured by a complete loss of AKT (Ser-473) phosphorylation in xenograft tumors grown in nude mice. Following a daily X5 dosing regimen, PWT-458 demonstrated single-agent antitumor activity in nude mouse xenograft models of U87MG glioma, non-small cell lung cancer (NSCLC) A549, and renal cell carcinoma (RCC) A498. Efficacious doses ranged from 0.5 mg/kg to 10 mg/kg, achieving a superior therapeutic index over 17-HWT. PWT-458 augmented anticancer efficacy of a suboptimal dose of paclitaxel against A549 and U87MG tumors. Combination treatment of PWT-458 and an mTOR inhibitor, Pegylated-Rapamycin (Peg-Rapa), resulted in an enhanced antitumor efficacy in U87MG. Finally, PWT-458 in combination with interferon-? (Intron-A) caused a dramatic regression of RCC A498, which was not achieved by either agent alone. These studies identify PWT-458 as an effective anticancer agent and provide strong proof-of-principle for targeting the PI3K pathway as novel anticancer therapy.

Hybrid Inhibitors of Phosphatidylinositol 3-Kinase (PI3K) and the Mammalian Target of Rapamycin (mTOR): Design, Synthesis, and Superior Antitumor Activity of Novel Wortmannin−Rapamycin Conjugates

Hyperactivation of the PI3K/AKT/mTOR signaling pathway is common in cancer, and PI3K and mTOR act synergistically in promoting tumor growth, survival, and resistance to chemotherapy. Thus, combined targeting of PI3K and mTOR presents an opportunity for robust and synergistic anticancer efficacy. 17-Hydroxywortmannin (2a) analogues conjugated to rapamycin (3a) analogues via a prodrug linker are uniquely positioned for this approach. Our efforts led to the discovery of diester-linked conjugates that, upon in vivo hydrolysis, released two highly potent inhibitors. Conjugate 7c provided enhanced solubility relative to 3a and to an equivalent mixture of 3a and 9a and demonstrated profound activity in U87MG mouse xenografts, achieving an MED of 1.5 mg/kg, following weekly intravenous dosing. At 15 mg/kg, 7c completely inhibited the growth of HT29 tumors, whereas an equivalent mixture of the inhibitors was poorly tolerated. In the A498 renal tumor model, 7c exhibited superior efficacy over 3a or 9a when administered as a single agent or in combination with bevacizumab. Thus, we have uncovered a novel approach to target both PI3K and mTOR via hybrid inhibitors, leading to a broader and more robust anticancer efficacy.

NMR structural analysis of the capsular polysaccharide from Streptococcus pneumoniae serotype 6C.

The original structure of Streptococcus pneumoniae capsular polysaccharide (CPS) serotype 6C was proposed based on chemical degradation and tandem mass analysis [J. Clin. Microbiol.2007, 45, 1225-1233]. In order to confirm the repeat unit structure and assign the stereochemical structure, the CPS 6C and the known CPS 6A were fully characterized by NMR spectroscopy. Full (1)H and (13)C NMR spectra assignments of CPS 6C and CPS 6A were achieved based on DQCOSY, TOCSY, HSQC, HMBC, and NOESY analysis. These analyses confirmed the published structure of CPS 6A and established the repeat unit structure of the CPS 6C as: →2)-α-D-Glcp-(1→3)-α-D-Glcp-(1→3)-α-L-Rhap-(1→3)-D-Ribitol-(5→phosphate-.