Synthesis and antitumor activity of novel C-7 paclitaxel ethers: discovery of BMS-184476.

The preparation of C-7 paclitaxel ethers is described. Various substituted ethers were prepared via activation of the corresponding methylthiomethyl ether followed by alcohol addition. Variation of the C-7 ether group as well the 3' side chain position led to the discovery of a novel taxane, BMS-184476 (4), with preclinical antitumor activity superior to paclitaxel.

Preclinical pharmacology of BMS-275183, an orally active taxane.

BMS-275183 is a taxane, the mechanism of action of which is like other known taxanes, and is the polymerization of tubulin. BMS-275183 given p.o. was as effective as i.v. paclitaxel in five tumor models [murine M109 lung and C3H mammary 16/C, and human A2780 ovarian (grown in mice and rats) and HCT/pk colon]. It was active in one other tumor model (human HCT-116 colon) but inferior to parenteral paclitaxel. BMS-275183 given p.o. was active in a human, hormone-dependent, prostate tumor model, CWR-22, and just as effective as anti-androgen chemotherapy. In a schedule dependency study, increasing the interval of time between oral administrations resulted in greater cumulative dose tolerance and improved therapeutic outcome. Oral BMS-275183 was evaluated as a combination therapy in conjunction with i.v. paclitaxel. Therapeutic advantages were evident for tumor-bearing mice that received the oral taxane either after induction chemotherapy or between courses of such treatment. BMS-275183 is currently in Phase I clinical trials at multiple sites.

Synthesis of a novel C-10 spiro-epoxide of paclitaxel.

New analogues of paclitaxel (1a, active constituent of Taxol) were synthesized containing an epoxide at the C-10 position. The introduction of the epoxide was carried out by selective removal of the C10-acetate followed by protection of the C2'- and C7-hydroxyl groups. After oxidation to yield a ketone at the C10-position, this intermediate was reacted with dimethylsulfonium ylide. Deprotection and further manipulations provide the C10-spiro epoxide of paclitaxel (1b) and the corresponding C7-MOM ether (1c).

Synthesis of metabolically blocked paclitaxel analogues.

The stereospecific syntheses of the metabolically blocked 6-alpha-F, Cl, Br paclitaxel, and 6-alpha-F-10-acetyldocetaxel are described and in vitro and in vivo activity is presented.

Synthesis and antitumor activity of novel paclitaxel-chlorambucil hybrids.

The syntheses and antitumor activity of three paclitaxel-chlorambucil hybrids are presented. Hybrid 3 showed significant in vivo efficacy.

Synthesis and bioactivity of 2,4-diacyl analogues of paclitaxel.

The 2,4-diacyl paclitaxel analogues 8a-8r were prepared from paclitaxel by acylation of 4-deacetyl-2-debenzoylpaclitaxel 1,2-carbonate (3) followed either by hydrolysis of the carbonate and acylation or by direct treatment of the carbonate with an aryllithium. Some of the resulting derivatives showed significantly improved tubulin assembly activity and cytotoxicity as compared with paclitaxel; in some cases this improvement was especially significant for paclitaxel-resistant cell lines.

Structure-activity relationships study at the 3'-N position of paclitaxel. Part 2: synthesis and biological evaluation of 3'-N-thiourea- and 3'-N-thiocarbamate-bearing paclitaxel analogues.

The syntheses and preliminary biological evaluation of 3'-N-thiocarbamate- and 3'-N-thiourea-bearing paclitaxel analogues, 4a-f and 5a-e, are described. 3'-N-thiocarbamates 4a-e were found to be more potent than paclitaxel in both the tubulin polymerization assay and the in vitro cytotoxicity assay. Several derivatives of this class such as 4c, 4d, and 4e also exhibited some in vivo activity.

Monoclonal antibody-beta-lactamase conjugates for the activation of a cephalosporin mustard prodrug.

Cephalosporin mustard (CM) was designed as an anticancer prodrug that could be activated in a site-specific manner by monoclonal antibody-beta-lactamase conjugates targeted to antigens present on tumor cell surfaces. Purified beta-lactamases from Bacillus cereus (BC beta L) and Escherichia coli (EC beta L) catalyzed the release of phenylenediamine mustard (PDM) from CM through a fragmentation reaction which occurs after the beta-lactam ring of CM is hydrolyzed. The Km and Vmax values were 5.7 microM and 201 mumol/min per mg for BC beta L and 43 microM and 29 mumol/min per mg for EC beta L, respectively. Conjugates of BC beta L were prepared by combining the F(ab')2 fragments of the maleimide-substituted monoclonal antibodies L6 and 1F5 with thiolated BC beta L. The conjugates showed little loss in enzymatic activity and bound nearly as well as the unmodified F(ab')2 monoclonal antibodies to antigens expressed on the H2981 human lung adenocarcinoma cell line (L6 positive, 1F5 negative). PDM was approximately 50-fold more cytotoxic than CM to H2981 cells. Treatment of the cells with L6-BC beta L followed by CM resulted in a level of cytotoxic activity that was comparable to that of PDM. This was most likely due to activation of CM by conjugate that bound to cell-surface antigens, since pretreatment of H2981 cells with BC beta L or 1F5-BC beta L enhanced the activity of CM to a lesser extent. Thus, we have shown that CM is a prodrug, and that it can be activated with immunological specificity by a monoclonal antibody-beta-lactamase conjugate.