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The persistence of genetic damage produced by alkylating agents 1 as well as the antagonism of essential biochemical processes such as transcription can have lethal consequences for malignant cells. 2 Both mechanisms have been identified in studies to uncover the reasons for the efficacy of cisplatin in the treatment of several cancers. 2a, 3 We describe a synthetic strategy to create bifunctional molecules that produce DNA adducts capable of binding the estrogen receptor (ER), which is aberrantly expressed in many breast cancer cells. 4 It is speculated that DNA adducts that form complexes with the ER will be poorly repaired in these cells because they are camouflaged from detection by DNA repair enzymes. Consequently, the DNA lesions persist. Furthermore, the DNA adducts would be expected to act as "molecular decoys" capable of displacing the ER from its natural targets and antagonizing its role in malignant growth. In healthy cells, where the abundance of the ER is minimal, no such ER-DNA adduct complexes will be present, and the cell should survive. 5 In this report we describe the design and synthesis of compound 1, a bifunctional agent that can form covalent DNA adducts capable of binding the ER with high affinity and specificity. We show that 1 has selective toxicity toward ER+ breast cancer cells compared to ER-cells in vitro.Compound 1 consists of a bis-chloroethyl aniline mustard as the DNA alkylating unit tethered to estradiol, the natural ligand for the ER. The site of substitution of estradiol in 1 was based on reports that relatively large alkyl groups can be attached at the 7α position with retention of high affinity for the ER 6 . The synthetic strategy for 1 is shown in Scheme 1. Compound 7, a key compound in the synthesis, was prepared by a modification of a published strategy. 7 Briefly, 3 was functionalized with a 6-carbon chain at the 7-position in α-stereochemistry to provide the alkenyl steroid 4. Efficient reduction of the 6-oxo group in 4 was achieved with Et 3 SiH/BF 3 .Et 2 O; however, this treatment also caused the loss of 3,17-tetrahydropyranoxy (THP) groups producing diol 5. The 3,17-OHs of 5 were reprotected with THP groups to afford 6, followed by oxidation of the alkene at the terminus of the linker to provide alcohol 7. Steroid alcohol 7 was converted to bromide 8, which was subsequently allowed to react with a protected ethanolamine to give 9. Compound 9 was desilylated with tetrabutylammonium fluoride (TBAF) and converted to a carbonate Next, the ability of 1 to modify DNA covalently was investigated. Plasmid DNA was incubated with 100 μM [ 14 C]-1 10 at 37 °C for up to 6 h. After unbound 1 was removed by phenol-CHCl 3 extraction and ethanol precipitation, the radioactivity associated with DNA was measured. The amount of radioactivity bound to DNA increased at a constant rate over the 6-h period indicating the formation of covalently bound 1 (see Supporting Information). Based on previous studies on DNA alkylation by nitrogen mustards, 11 it is likely that covalent adducts of...

We describe successful efforts to optimize the in vivo profile and address off-target liabilities of a series of BACE1 inhibitors represented by 6 that embodies the recently validated fused pyrrolidine iminopyrimidinone scaffold. Employing structure-based design, truncation of the cyanophenyl group of 6 that binds in the S3 pocket of BACE1 followed by modification of the thienyl group in S1 was pursued. Optimization of the pyrimidine substituent that binds in the S2'-S2″ pocket of BACE1 remediated time-dependent CYP3A4 inhibition of earlier analogues in this series and imparted high BACE1 affinity. These efforts resulted in the discovery of difluorophenyl analogue 9 (MBi-4), which robustly lowered CSF and cortex Aβ40 in both rats and cynomolgus monkeys following a single oral dose. Compound 9 represents a unique molecular shape among BACE inhibitors reported to potently lower central Aβ in nonrodent preclinical species.

The goal of our work was the design of DNA-damaging agents that disrupt both DNA repair and signaling pathways in prostate tumor cells. A DNA alkylator (N,N-bis-2-chloroethyl aniline) was linked to a steroid ligand (17beta-hyroxy-estra-Delta(4(5),9(10))-3-one) to produce a complex molecule (11beta-dichloro) that forms DNA adducts that bind the androgen receptor (AR). We speculated that DNA adducts in an AR-DNA adduct complex would be camouflaged from DNA repair proteins that would otherwise remove the adducts in prostate cancer cells. Furthermore, transcription dependent on the AR would be antagonized by AR redistribution to sites distant from AR-driven promoters. The anticancer potential of 11beta-dichloro was demonstrated against prostate cancer cells in vitro and in vivo. 11beta-dichloro induces a unique pattern of gene disruption, induces apoptosis in apoptosis-resistant cells, and shows promising anticancer activity in animals.

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