Kosan Biosciences, Inc. (stock symbol: KOSN), was a pharmaceutical company which dealt with cancer therapeutics medications. The company was working on advancing two new classes of anticancer agents through clinical development: heat shock protein 90 (Hsp90) inhibitors and epothilones.Their technology platform was based on manipulation of the genetic instructions of microbes for making natural product polyketides. Rearranging the modular units in natural polyketide synthases, combining modules from different enzymes, and incorporating novel synthetic chemical starter units enabled them to produce a wide variety of novel polyketides that would be difficult to obtain via organic synthesis alone.Founded in 1995, Kosan was headquartered in Hayward, California and had approximately 90 employees. Kosan was funded in part as a venture capital start-up with funds from Sofinnova Ventures of California.On June 26, 2008, Kosan Biosciences was acquired by Bristol-Myers Squibb for $190M.
Allylalumination of alkynes (i.e. forming Negishi's (Z)-alkenyl dialkylalane) followed by alkenylation of epoxides provides 1,4-disubstituted (Z)-3,6-alkadienols. The alkenylation can be facilitated by the presence of a neighbouring coordinating group in the epoxides. This "one-pot" approach has been successfully applied in the large-scale production of C10-C15 fragment of 9,10-didehydroepothilone D (a synthetic epothilone analog as an anti-cancer agent in phase 2 clinical trials).
Abstract Purpose: HSP90 is a chaperone protein required for the stability of a variety of client proteins. 17-Demethoxygeldanamycin (17-AAG) is a natural product that binds to HSP90 and inhibits its activity, thereby inducing the degradation of these clients. In preclinical studies, HER2 is one of the most sensitive known client proteins of 17-AAG. On the basis of these data and activity in a phase I study, we conducted a phase II study of 17-AAG (tanespimycin) with trastuzumab in advanced trastuzumab-refractory HER2-positive breast cancer. Experimental Design: We enrolled patients with metastatic HER2+ breast cancer whose disease had previously progressed on trastuzumab. All patients received weekly treatment with tanespimycin at 450 mg/m2 intravenously and trastuzumab at a conventional dose. Therapy was continued until disease progression. The primary endpoint was response rate by Response Evaluation Criteria in Solid Tumors (RECIST) criteria. Results: Thirty-one patients were enrolled with a median age of 53 years and a median Karnofsky performance status (KPS) of 90%. The most common toxicities, largely grade 1, were diarrhea, fatigue, nausea, and headache. The overall response rate was 22%, the clinical benefit rate [complete response + partial response + stable disease] was 59%, the median progression-free survival was 6 months (95% CI: 4–9), and the median overall survival was 17 months (95% CI: 16–28). Conclusions: This is the first phase II study to definitively show RECIST-defined responses for 17-AAG in solid tumors. Tanespimycin plus trastuzumab has significant anticancer activity in patients with HER2-positive, metastatic breast cancer previously progressing on trastuzumab. Further research exploring this therapeutic interaction and the activity of HSP90 inhibitors is clearly warranted. Clin Cancer Res; 17(15); 5132–9. ©2011 AACR.
The role of the erythromycin 4′′-hydroxyl group has been explored on the motilin agonist potential in the 9-dihydroerythromycin series of motilides. The compounds show potencies 2- to 4-fold superior to the corresponding hydroxylated compounds. The relationship is maintained when the 9-hydroxyl is alkylated to generate the corresponding 4′′-deoxy-9-O-acetamido-9-dihydroerythromycins. However, concomitant with this increase in potency is an increase in hERG inhibition.
Heat shock protein 90 (Hsp90) is a molecular chaperone with many oncogenic client proteins. The small-molecule Hsp90 inhibitor alvespimycin, a geldanamycin derivative, is being developed for various malignancies. This phase 1 study examined the maximum-tolerated dose (MTD), safety and pharmacokinetic/pharmacodynamic profiles of alvespimycin in patients with advanced acute myeloid leukemia (AML). Patients with advanced AML received escalating doses of intravenous alvespimycin (8–32 mg/m2), twice weekly, for 2 of 3 weeks. Dose-limiting toxicities (DLTs) were assessed during cycle 1. A total of 24 enrolled patients were evaluable for toxicity. Alvespimycin was well tolerated; the MTD was 24 mg/m2 twice weekly. Common toxicities included neutropenic fever, fatigue, nausea and diarrhea. Cardiac DLTs occurred at 32 mg/m2 (elevated troponin and myocardial infarction). Pharmacokinetics revealed linear increases in Cmax and area under the curve (AUC) from 8 to 32 mg/m2 and minor accumulation upon repeated doses. Pharmacodynamic analyses on day 15 revealed increased apoptosis and Hsp70 levels when compared with baseline within marrow blasts. Antileukemia activity occurred in 3 of 17 evaluable patients (complete remission with incomplete blood count recovery). The twice-weekly administered alvespimycin was well tolerated in patients with advanced AML, showing linear pharmacokinetics, target inhibition and signs of clinical activity. We determined a recommended phase 2 dose of 24 mg/m2.
ABSTRACT In vivo reconstitution of the TDP- l -megosamine pathway from the megalomicin gene cluster of Micromonospora megalomicea was accomplished by the heterologous expression of its biosynthetic genes in Escherichia coli. Mass spectrometric analysis of the TDP-sugar intermediates produced from operons containing different sets of genes showed that the production of TDP- l -megosamine from TDP-4-keto-6-deoxy- d -glucose requires only five biosynthetic steps, catalyzed by MegBVI, MegDII, MegDIII, MegDIV, and MegDV. Bioconversion studies demonstrated that the sugar transferase MegDI, along with the helper protein MegDVI, catalyzes the transfer of l -megosamine to either erythromycin C or erythromycin D, suggesting two possible routes for the production of megalomicin A. Analysis in vivo of the hydroxylation step by MegK indicated that erythromycin C is the intermediate of megalomicin A biosynthesis.
