Cryptophycins-309, 249 and other cryptophycin analogs: preclinical efficacy studies with mouse and human tumors.

Cryptophycins-1 and 52 (epoxides) were discovered to have in-vitro and in-vivo antitumor activity in the early 1990s. The chlorohydrins of these, Cryptophycins-8 and 55 (also discovered in the early 1990s) were markedly more active, but could not be formulated as stable solutions. With no method to adequately stabilize the chlorohydrins at the time, Cryptophycin-52 (LY 355073) entered clinical trials, producing only marginal antitumor activity. Since that time, glycinate esters of the hydroxyl group of the chlorohydrins have been synthesized and found to provide stability. Three of the most active were compared herein. Cryptophycin-309 (C-309) is a glycinate ester of the chlorohydrin Cryptophycin-296. The glycinate derivative provided both chemical stability and improved aqueous solubility. After the examination of 81 different Cryptophycin analogs in tumor bearing animals, C-309 has emerged as superior to all others. The following %T/C and Log Kill (LK) values were obtained from a single course of IV treatment (Q2d x 5) against early staged SC transplantable tumors of mouse and human origin: Mam 17/Adr [a pgp (+) MDR tumor]: 0%T/C, 3.2 LK; Mam 16/C/Adr [a pgp (-) MDR tumor]: 0%T/C, 3.3 LK; Mam 16/C: 0%T/C, 3.8 LK; Colon 26: 0%T/C, 2.2 LK; Colon 51: 0%T/C, 2.4 LK; Pancreatic Ductal Adenocarcinoma 02 (Panc 02): 0%T/C, 2.4 LK; Human Colon HCT15 [a pgp (+) MDR tumor]: 0%T/C, 3.3 LK; Human Colon HCT116: 0%T/C, 4.1 LK. One additional analog, Cryptophycin-249 (C-249, the glycinate of Cryptophycin-8), also emerged with efficacy rivaling or superior to C-309. However, there was sufficient material for only a single C-249 trial in which a 4.0 LK was obtained against the multidrug resistant breast adenocarcinoma Mam-16/C/Adr. C-309 and C-249 are being considered as second-generation clinical candidates.

Biological evaluation of cryptophycin 52 fragment A analogues: effect of the multidrug resistance ATP binding cassette transporters on antitumor activity.

Cryptophycin 52 (LY355703) is a potent antiproliferative analogue of the marine natural product cryptophycin 1. It has been shown to have a broad range of antitumor activity against human tumor xenografts and murine tumors including tumors resistant to Taxol and Adriamycin. Its mechanism of action involves arresting cells in the G2-M phase of the cell cycle by binding to microtubules and suppressing their dynamics. This 16-membered depsipeptide can be divided into four major subunits or fragments (A-D). We reported previously on our synthetic efforts around fragment A and discovered that this region of the molecule was amenable to a structure-activity relationship study that resulted in highly active antiproliferative agents when evaluated in the CEM leukemia cell line. The synthetic analogues were designed to help improve the efficacy and aqueous solubility of the parent compound; therefore, many in this series contained ionizable functional groups such as an amino group, a hydroxy group, or a carboxylic acid. Although several of these analogues showed improvements in potency over cryptophycin 52 in drug-sensitive tumor xenograft models, many lost their activity against Adriamycin-resistant tumor lines. It was discovered on additional in vitro evaluation that these analogues became good substrates of the multidrug resistance transporter P-glycoprotein.

Preparation of novel aza-1,7-annulated indoles and their conversion to potent indolocarbazole kinase inhibitors.

The synthesis of novel aza-1,7-annulated indoles was achieved and these were converted to indolocarbazoles that proved to be potent kinase inhibitors. These compounds were also evaluated in a human colon carcinoma cell line and proved to be good antiproliferative agents.

1,7-annulated indolocarbazoles as cyclin-dependent kinase inhibitors.

The synthesis and kinase inhibitory activity of a series of novel 1,7-annulated indolocarbazoles 6 and 16 is described. These compounds exhibited potent inhibitory activity against cyclin-dependent kinase 4 and good antiproliferative activity in a human colon carcinoma cell line.

Synthetic approaches to indolo[6,7-a]pyrrolo[3,4-c]carbazoles: potent cyclin D1/CDK4 inhibitors.

Synthesis of indolo[6,7-a]pyrrolo[3,4-c]carbazoles 1, a new class of cyclin D1/CDK4 inhibitors, by oxidation of the corresponding aryl indolylmaleimides 2, will be described. Two approaches to the synthesis of 2 were identified that required new methods for the synthesis of 7-substituted indole acetamides 3 and N-methyl (indol-7-yl)oxoacetates 6. The chemistry developed enabled introduction of functionality (-OR, NR(2)) at C(12) and N(13) facilitating structure-activity relationship (SAR) evaluation of this indolocarbazole platform.

A convergent approach to cryptophycin 52 analogues: synthesis and biological evaluation of a novel series of fragment a epoxides and chlorohydrins.

Cryptophycin 52 is a synthetic derivative of Cryptophycin 1, a potent antimicrotubule agent isolated from cyanobacteria. In an effort to increase the potency and water solubility of the molecule, a structure-activity relationship study (SAR) was initiated around the phenyl ring of fragment A. These Cryptophycin 52 analogues were accessed using a Wittig olefination reaction between various triphenylphosphonium salts and a key intermediate aldehyde prepared from Cryptophycin 53. Substitution on the phenyl ring of fragment A was well tolerated, and several of these analogues were equally or more potent than Cryptophycin 52 when evaluated in vitro in the CCRF-CEM leukemia cell line and in vivo against a murine pancreatic adenocarcinoma.