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, nonsmall 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-alpha (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.

Phosphoinositide 3-kinase (PI3K) is an important target for cancer chemotherapy due to the deregulation of its signaling pathway in a wide spectrum of human tumors. Wortmannin and its analogues are potent PI3K inhibitors whose therapeutic use has been impeded by inherent defects such as instability and toxicity. Pegylation of wortmannin and 17-hydroxywortmannin gives rise to conjugates with improved properties, including a higher therapeutic index. Pegylated 17-hydroxywortmannin (8, PWT-458) has been selected for further development.

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Tobramycin is an aminoglycoside antibiotic that loses a significant amount of activity in the presence of Zosyn at pH 6. As part of our investigation into ways to improve the compatibility of tobramycin with Zosyn (which contains piperacillin and tazobactam in an 8:1 ratio buffered at pH 6 by sodium citrate) by lowering the pH, we identified the reaction product of tobramycin and piperacillin at pH 6.0 and the order of the pK a values of tobramycin. The structure of the main reaction product of tobramycin and piperacillin at pH 6.0 was determined by 2D NMR to be the product of 3 00 -NH 2 reacting with the b-lactam of piperacillin. The order of the pK a values of the nitrogens of tobramycin was determined by 1 H and 15 N NMR titrations to be 6¢-NH 2 42¢-NH 2 41-NH 2 E3 00 -NH 2 43-NH 2 . At pH 4.0, the reaction between tobramycin and Zosyn was almost negligible for a period of up to 2 h. The pH can be lowered by adding an acid such as HCl or citric acid to Zosyn to make a pH 4.0 buffer. The Journal of Antibiotics (2011) 64, 673-677; doi:10.1038/ja.2011.72; published online 3 August 2011Keywords: piperacillin; protonation constants; structure elucidation; tobramycin; Y-site co-administration; Zosyn INTRODUCTION Tobramycin (Figure 1) is an aminoglycoside antibiotic produced by Streptomyces tenebrarius 1 used to treat infections caused by susceptible Gram-negative microorganisms. 2 It is often used in combination with penicillins, such as piperacillin (Figure 2), to treat severe infections caused by Gram-negative bacteria. 3 It is well known that tobramycin reacts with b-lactams, including piperacillin, causing a significant loss of aminoglycoside activity. 4 The inactivation mechanism is thought to involve nucleophilic attack and ring opening of the penicillin b-lactam ring by an amino group of the aminoglycoside. 5,6 The rate of aminoglycoside inactivation is dependent on temperature, time, concentration of the b-lactam and composition of the medium. [7][8][9] Another important factor to consider is the pH of the solution. As the degree of protonation of an amino group increases, it should become less nucleophilic. The amino groups of tobramycin have different pK a values, 10,11 hence, it is logical to assume the reaction would be affected by pH of the solution. Therefore, knowledge of the protonation constants of the amino groups and their order is important in understanding the reactivity of tobramycin with piperacillin at different pHs.Zosyn is an intravenously administered antibiotic, which contains piperacillin and tazobactam (a b-lactamase inhibitor) in an 8:1 ratio. It also contains EDTA and sodium citrate, which is used to buffer the solution at around pH 6. 12 It has been approved for Y-site coadministration with the aminoglycosides amikacin and gentamicin. 13 It has not been approved for co-administration with tobramycin,

Production of carious lesions has long been associated with an attack of the enamel by various acids produced by the bacteria of the mouth (10-16). A simple model (1) was