Phase I dose escalation study of the PI3kinase pathway inhibitor BKM120 and the oral poly (ADP ribose) polymerase (PARP) inhibitor olaparib for the treatment of high-grade serous ovarian and breast cancer.

Background: Based upon preclinical synergy in murine models, we carried out a phase I trial to determine the maximum tolerated dose (MTD), toxicities, pharmacokinetics, and biomarkers of response for the combination of BKM120, a PI3K inhibitor, and olaparib, a PARP inhibitor. Patients and methods: Olaparib was administered twice daily (tablet formulation) and BKM120 daily on a 28-day cycle, both orally. A 3 + 3 dose-escalation design was employed with the primary objective of defining the combination MTD, and secondary objectives were to define toxicities, activity, and pharmacokinetic profiles. Eligibility included recurrent breast (BC) or ovarian cancer (OC); dose-expansion cohorts at the MTD were enrolled for each cancer. Results: In total, 69 of 70 patients enrolled received study treatment; one patient never received study treatment because of ineligibility. Twenty-four patients had BC; 46 patients had OC. Thirty-five patients had a germline BRCA mutation (gBRCAm). Two DLTs (grade 3 transaminitis and hyperglycemia) were observed at DL0 (BKM120 60 mg/olaparib and 100 mg b.i.d.). The MTD was determined to be BKM120 50 mg q.d. and olaparib 300 mg b.i.d. (DL8). Additional DLTs included grade 3 depression and transaminitis, occurring early in cycle 2 (DL7). Anticancer activity was observed in BC and OC and in gBRCAm and gBRCA wild-type (gBRCAwt) patients. Conclusions: BKM120 and olaparib can be co-administered, but the combination requires attenuation of the BKM120 dose. Clinical benefit was observed in both gBRCAm and gBRCAwt pts. Randomized phase II studies will be needed to further define the efficacy of PI3K/PARP-inhibitor combinations as compared with a PARP inhibitor alone.

Screening of 14C-polyamines in the AT3B-1 rat prostate tumor model: the search for a new PET prostate imaging agent.

BACKGROUND: We have previously reported the polyamine uptake kinetics in various prostate and non-prostate cancer cell lines, concluding that the prostate cancer cell lines took up and accumulated polyamines at higher levels than non-prostate cell lines, with a view to their use as PET agents. The objective of the present study was to assess their in vivo accumulation in a rat prostate tumor model. MATERIALS AND METHODS: A comparative biodistribution study of the polyamines was conducted in AT3B-1 prostate tumors in male Copenhagen rats to determine which of the polyamines show preferential accumulation in the tumor. Tissue samples were collected one hour post administration of the polyamines (i.v.), and the radioactivity of the samples was measured by first combusting the tissue samples in a biological oxidizer and then assaying the trapped 14CO2 in a liquid scintillation counter. RESULTS: Putrescine exhibited the highest tumor accumulation followed by ornithine (4.1% and 1.8% of injected dose/g of the tumor respectively). The tumor-to-blood ratio was highest with putrescine followed by spermidine (18.7 and 12.9 respectively) and the order of tumor-to-normal prostate accumulation ratio was putrescine>ornithine>spermine>spermidine. CONCLUSION: The results indicated preferential accumulation of putrescine and ornithine in the prostate tumor.

Anticancer effects of thiazolidinediones are independent of peroxisome proliferator-activated receptor gamma and mediated by inhibition of translation initiation.

The thiazolidinedione (TZD) class of peroxisome proliferator-activated receptor (PPAR) gamma ligands, known for their ability to induce adipocyte differentiation and increase insulin sensitivity, also exhibits anticancer properties. Currently, TZDs are being tested in clinical trials for treatment of human cancers expressing high levels of PPARgamma because it is assumed that activation of PPARgamma mediates their anticancer activity. Using PPARgamma(-/-) and PPARgamma(+/+) mouse embryonic stem cells, we report here that inhibition of cell proliferation and tumor growth by TZDs is independent of PPARgamma. Our studies demonstrate that these compounds block G(1)-S transition by inhibiting translation initiation. Inhibition of translation initiation is the consequence of partial depletion of intracellular calcium stores and the resulting activation of protein kinase R that phosphorylates the alpha subunit of eukaryotic initiation factor 2 (eIF2), thus rendering eIF2 inactive. PPARgamma-independent inhibition of translation initiation most likely accounts for the anticancer properties of thiazolidinediones.

Inhibition of translation initiation mediates the anticancer effect of the n-3 polyunsaturated fatty acid eicosapentaenoic acid.

Eicosapentaenoic acid (EPA), an n-3 polyunsaturated fatty acid that is abundant in the fish-based diets of populations that exhibit a remarkably low incidence of cancer, exerts anticancer activity in vitro and in animal models of experimental cancer. Here we define the molecular basis for the anticancer effects of EPA. EPA inhibits cell division by inhibiting translation initiation. This is a consequence of the ability of EPA to release Ca2+ from intracellular stores while inhibiting their refilling via capacitative Ca2+ influx that results in partial emptying of intracellular Ca2+ stores and thereby activation of protein kinase R. Protein kinase R phosphorylates and inhibits eukaryotic initiation factor 2alpha, resulting in inhibition of protein synthesis at the level of translation initiation, preferentially reducing the synthesis and expression of growth-regulatory proteins, including G1 cyclins, and causes cell cycle arrest in G1. In a KLN-205 squamous cell carcinoma mouse model, daily oral administration of EPA resulted in a significant reduction of tumor size and expression of cyclin D1 in the tumor tissues. Furthermore, EPA-treated tumors showed a significant increase in the proportion of diploid cells, indicative of cell cycle arrest in G0-G1, and a significant reduction of malignant hypertetraploid cells. These results characterize EPA as a member of an emerging new class of anticancer compounds that inhibit translation initiaton.

Biodisposition of PEG-coated lipid microspheres of indomethacin in arthritic rats.

Conventional lipid microspheres (LM) were prepared using soybean oil and lipid at a 5.5:1 weight ratio with lipid phase consisting of PC (phosphatidyl choline):CH (cholesterol) (1:0.5) by molar ratio. The average diameter of the particles was 150 nm. Long-circulating microspheres (S-LM) were also prepared similarly but the lipid phase consisted of PC:CH:DSPE-PEG (phosphatidyl choline:cholesterol:distearoyl phosphatidyl ethanolamine-polyethylene glycol) 1:0.5:0.16 by molar ratio. A comparative biodistribution study was conducted between free indomethacin and lipo-indomethacin (LM and S-LM) in the arthritic rats by administering the formulations at a dose equivalent to 12 mg of indomethacin/kg. It was observed that the free drug as well as the encapsulated drug followed biphasic clearance from the blood. Pharmacokinetic parameters, such as AUC(0-t), terminal half-life, MRT increased significantly when the drug was used in encapsulated form (p < 0.05). Clearance of the drug was reduced 1.4 times with the conventional lipid microspheres and was reduced three-fold when encapsulated in polyethylene glycol-coated lipid microspheres. The overall drug targeting efficiency (T(e)) with the PEG-coated lipid microspheres was 7.5-fold higher than the conventional lipid microspheres. The high accumulation of the drug in arthritic paw with S-LM system may be accounted for by the reduced uptake by RES cells, and thereby, availability for extravascularization in the inflammatory tissues.

Biodistribution of liposomes of terbutaline sulfate in guinea pigs.

A series of liposomes was prepared with various lipid (egg phosphatidyl choline [egg PC], phosphatidyl glycerol [PG], dipalmitoyl phosphatidyl choline [DPPC], distearoyl phosphatidyl choline [DSPC], dipalmitoyl phosphatidyl glycerol [DPPG], phosphatidyl ethanolamine [PE], cholesterol [CH], and stearylamine [SA]) compositions, such as egg PC:PG:CH (55:5:40), DPPC:PG:CH (55:5:40), DSPC:DSPG:CH (55:5:40) egg PC:SA:CH (55:5:40), DSPE:DSPG:CH (55:5:40) in molar ratio. Liposomal formulations were administered to guinea pigs intravenously; 3 hr after the treatment, serum samples and various organs (e.g., liver, spleen, lung) were removed and analyzed for drug concentration by a high-performance liquid chromatographic (HPLC) method. Based on the above study, a liposomal preparation with better lung specificity was selected, and the time profile of these liposomes was determined in guinea pigs. Three hours postadministration, a significant difference in blood levels was observed between free terbutaline sulfate and the various liposomal formulations. Localization of the drug in the lungs increased considerably when encapsulated drug was used, and the highest percentage localization was observed with DSPC:DSPG:CH (55:5:40) liposomes. The percentage recovery of the drug in the lungs with egg PC:CH:SA (55:40:5) liposomes did not change significantly when compared with egg PC:CH:PG (55:40:5) liposomes. To establish the time course of disposition of the liposomes, DSPC:DSPG:CH (55:5:40) liposomes were selected. Terminal half-life t1/2 of the drug in blood with free drug solution was about 12 hr, whereas with liposomes, a twofold increase in t1/2 was observed. The disposition data indicated that the clearance of the drug was delayed by 1.5 times when incorporated into liposomes.

Depletion of intracellular Ca2+ stores, phosphorylation of eIF2alpha, and sustained inhibition of translation initiation mediate the anticancer effects of clotrimazole.

Regulation of translation initiation plays a critical role in the control of cell growth and division in eukaryotic cells. Translation of many growth regulatory proteins including cyclins depends critically on translation initiation factors because their mRNAs are translated inefficiently. We report that clotrimazole, a potent antiproliferative agent both in vitro and in vivo, inhibits cell growth by interfering with translation initiation. In particular, clotrimazole causes a sustained depletion of intracellular Ca2+ stores, which results in activation of PKR, phosphorylation of eIF2alpha, and thereby in inhibition of protein synthesis at the level of translation initiation. Consequently, clotrimazole preferentially decreases the expression of the growth promoting proteins cyclin A, E and D1, resulting in inhibition of cyclin-dependent kinase activity and blockage of cell cycle in G1.