We have designed, synthesized, and evaluated a series of new compounds based upon our previously reported bivalent Smac mimetics. This led to the identification of compound 12 (SM-1200), which binds to XIAP, cIAP1, and cIAP2 with Ki values of 0.5, 3.7, and 5.4 nM, respectively, inhibits cell growth in the MDA-MB-231 breast cancer and SK-OV-3 ovarian cancer cell lines with IC50 values of 11.0 and 28.2 nM, respectively. Compound 12 has a much improved pharmacokinetic profile over our previously reported bivalent Smac mimetics and is highly effective in induction of rapid and durable tumor regression in the MDA-MB-231 xenograft model. These data indicate that compound 12 is a promising Smac mimetic and warrants extensive evaluation as a potential candidate for clinical development.

We have designed and synthesized 9H-pyrimido[4,5-b]indole-containing compounds to obtain potent and orally bioavailable BET inhibitors. By incorporation of an indole or a quinoline moiety to the 9H-pyrimido[4,5-b]indole core, we identified a series of small molecules showing high binding affinities to BET proteins and low nanomolar potencies in inhibition of cell growth in acute leukemia cell lines. One such compound, 4-(6-methoxy-2-methyl-4-(quinolin-4-yl)-9H-pyrimido[4,5-b]indol-7-yl)-3,5-dimethylisoxazole (31) has excellent microsomal stability and good oral pharmacokinetics in rats and mice. Orally administered, 31 achieves significant antitumor activity in the MV4;11 leukemia and MDA-MB-231 triple-negative breast cancer xenograft models in mice. Determination of the cocrystal structure of 31 with BRD4 BD2 provides a structural basis for its high binding affinity to BET proteins. Testing its binding affinities against other bromodomain-containing proteins shows that 31 is a highly selective inhibitor of BET proteins. Our data show that 31 is a potent, selective, and orally active BET inhibitor.

Aberrant PRC2 activity produces gene repressive epigenetic marks in multiple diseases and led to identification of Ezh2 as a drug target. Recent studies have shown that the epigenetic reader protein EED, associated with Ezh2 in PRC2, has an additional function to stimulate the PRC2 activity after binding to H3K27me3. Optimizing a compound known to block the H3K27me3 site in EED discovered by in-house screening, Novartis scientists have now produced a compound that shows durable tumor regression in a lymphoma xenograft model.

We report herein the design, synthesis, and evaluation of macrocyclic peptidomimetics that bind to WD repeat domain 5 (WDR5) and block the WDR5–mixed lineage leukemia (MLL) protein–protein interaction. Compound 18 (MM-589) binds to WDR5 with an IC50 value of 0.90 nM (Ki value <1 nM) and inhibits the MLL H3K4 methyltransferase (HMT) activity with an IC50 value of 12.7 nM. Compound 18 potently and selectively inhibits cell growth in human leukemia cell lines harboring MLL translocations and is >40 times better than the previously reported compound MM-401. Cocrystal structures of 16 and 18 complexed with WDR5 provide structural basis for their high affinity binding to WDR5. Additionally, we have developed and optimized a new AlphaLISA-based MLL HMT functional assay to facilitate the functional evaluation of these designed compounds. Compound 18 represents the most potent inhibitor of the WDR5–MLL interaction reported to date, and further optimization of 18 may yield a new therapy for acute leukemia.

We previously reported the design of spirooxindoles with two identical substituents at the carbon-2 of the pyrrolidine core as potent MDM2 inhibitors. In this paper we describe an extensive structure–activity relationship study of this class of MDM2 inhibitors, which led to the discovery of 60 (AA-115/APG-115). Compound 60 has a very high affinity to MDM2 (Ki < 1 nM), potent cellular activity, and an excellent oral pharmacokinetic profile. Compound 60 is capable of achieving complete and long-lasting tumor regression in vivo and is currently in phase I clinical trials for cancer treatment.

Shelterin, a six-protein complex, plays a fundamental role in protecting both the length and the stability of telomeres. Repressor activator protein 1 (RAP1) and telomeric repeat-binding factor 2 (TRF2) are two subunits in shelterin that interact with each other. Small-molecule inhibitors that block the RAP1/TRF2 protein–protein interaction can disrupt the structure of shelterin and may be employed as pharmacological tools to investigate the biology of shelterin. On the basis of the cocrystal structure of RAP1/TRF2 complex, we have developed first-in-class triazole-stapled peptides that block the protein–protein interaction between RAP1 and TRF2. Our most potent stapled peptide binds to RAP1 protein with a Ki value of 7 nM and is >100 times more potent than the corresponding wild-type TRF2 peptide. On the basis of our high-affinity peptides, we have developed and optimized a competitive, fluorescence polarization (FP) assay for accurate and rapid determination of the binding affinities of our designed compounds and this assay may also assist in the discovery of non-peptide, small-molecule inhibitors capable of blocking the RAP1/TRF2 protein–protein interaction.

Design of small-molecule inhibitors (MDM2 inhibitors) to block the MDM2–p53 protein–protein interaction has been pursued as a new cancer therapeutic strategy. In recent years, potent, selective, and efficacious MDM2 inhibitors have been successfully obtained and seven such compounds have been advanced into early phase clinical trials for the treatment of human cancers. Here, we review the design, synthesis, properties, preclinical, and clinical studies of these clinical-stage MDM2 inhibitors.

Small-molecule inhibitors of bromodomain and extra terminal proteins (BET), including BRD2, BRD3, and BRD4 proteins have therapeutic potential for the treatment of human cancers and other diseases and conditions. In this paper, we report the design, synthesis, and evaluation of γ-carboline-containing compounds as a new class of small-molecule BET inhibitors. The most potent inhibitor (compound 18, RX-37) obtained from this study binds to BET bromodomain proteins (BRD2, BRD3, and BRD4) with Ki values of 3.2–24.7 nM and demonstrates high selectivity over other non-BET bromodomain-containing proteins. Compound 18 potently and selectively inhibits cell growth in human acute leukemia cell lines harboring the rearranged mixed lineage leukemia 1 gene. We have determined a cocrystal structure of 18 in complex with BRD4 BD2 at 1.4 Å resolution, which provides a solid structural basis for the compound’s high binding affinity and for its further structure-based optimization. Compound 18 represents a promising lead compound for the development of a new class of therapeutics for the treatment of human cancer and other conditions.

We described herein structure-based design, synthesis and evaluation of conformationally constrained, cyclic peptidomimetics to block the MLL1-WDR5 protein–protein interaction as inhibitors of the MLL1 histone methyltransferase activity. Our study has yielded cyclic peptidomimetics with very high binding affinities to WDR5 (Ki values <1 nmol/L) and function as antagonists of the MLL1 histone methyltransferase activity.Structure-based design, synthesis and evaluation of high-affinity, conformationally constrained peptidomimetics as inhibitors of the WDR5-MLL1 protein–protein interaction and MLL1 methyltransferase activity are described.

Inhibition of the MDM2–p53 protein–protein interaction is being actively pursued as a new anticancer therapeutic strategy, and spiro-oxindoles have been designed as a class of potent and efficacious small-molecule inhibitors of this interaction (MDM2 inhibitors). Our previous study showed that some of our first-generation spiro-oxindoles undergo a reversible ring-opening-cyclization reaction that, from a single compound in protic solution, results in an equilibrium mixture of four diastereoisomers. By exploiting the ring-opening-cyclization reaction mechanism, we have designed and synthesized a series of second-generation spiro-oxindoles with symmetrical pyrrolidine C2 substitution. These compounds undergo a rapid and irreversible conversion to a single, stable diastereoisomer. Our study has yielded compound 31 (MI-1061), which binds to MDM2 with Ki = 0.16 nM, shows excellent chemical stability, and achieves tumor regression in the SJSA-1 xenograft tumor model in mice.

Cellular inhibitor of apoptosis protein 1 and 2 (cIAP1/2) and X-linked inhibitor of apoptosis protein (XIAP) are key apoptosis regulators and promising new cancer therapeutic targets. This study describes a set of non-peptide, small-molecule Smac (second mitochondria-derived activator of caspases) mimetics that are selective inhibitors of cIAP1/2 over XIAP. The most potent and most selective compounds bind to cIAP1/2 with affinities in the low nanomolar range and show >1,000-fold selectivity for cIAP1 over XIAP. These selective cIAP inhibitors effectively induce degradation of the cIAP1 protein in cancer cells at low nanomolar concentrations and do not antagonize XIAP in a cell-free functional assay. They potently inhibit cell growth and effectively induce apoptosis at low nanomolar concentrations in cancer cells with a mechanism of action similar to that of other known Smac mimetics. Our study shows that binding of Smac mimetics to XIAP BIR3 is not required for effective induction of apoptosis in tumor cells by Smac mimetics. These potent and highly selective cIAP1/2 inhibitors are powerful tools in the investigation of the role of these IAP proteins in the regulation of apoptosis and other cellular processes.

Small-molecule inhibitors that block the MDM2-p53 protein–protein interaction (MDM2 inhibitors) are being intensely pursued as a new therapeutic strategy for cancer treatment. We previously published a series of spirooxindole-containing compounds as a new class of MDM2 small-molecule inhibitors. We report herein a reversible ring-opening-cyclization reaction for some of these spirooxindoles, which affords four diastereomers from a single compound. Our biochemical binding data showed that the stereochemistry in this class of compounds has a major effect on their binding affinities to MDM2, with >100-fold difference between the most potent and the least potent stereoisomers. Our study has led to the identification of a set of highly potent MDM2 inhibitors with a stereochemistry that is different from that of our previously reported compounds. The most potent compound (MI-888) binds to MDM2 with a Ki value of 0.44 nM and achieves complete and long-lasting tumor regression in an animal model of human cancer.

Bromodomain and extra-terminal (BET) proteins belong to a class of proteins collectively called epigenetic “readers”. BET bromodomains have emerged as promising drug targets for treatment of cancers, inflammatory diseases, and other medical conditions. GlaxoSmithKline scientists have successfully optimized a class of benzodiazepines as inhibitors of BET bromodomains, without any prior knowledge of identified molecular targets. It thus is possible to hit a target without aiming at it. The optimized lead compound I-BET762 is currently being evaluated in a phase I clinical trial for treatment of human cancer.

We previously reported the discovery of a class of spirooxindoles as potent and selective small-molecule inhibitors of the MDM2–p53 interaction (MDM2 inhibitors). We report herein our efforts to improve their pharmacokinetic properties and in vivo antitumor activity. Our efforts led to the identification of 9 (MI-888) as a potent MDM2 inhibitor (Ki = 0.44 nM) with a superior pharmacokinetic profile and enhanced in vivo efficacy. Compound 9 is capable of achieving rapid, complete, and durable tumor regression in two types of xenograft models of human cancer with oral administration and represents the most potent and efficacious MDM2 inhibitor reported to date.

Menin is an essential oncogenic cofactor for mixed lineage leukemia 1 (MLL1)-mediated leukemogenesis through its direct interaction with MLL1. Targeting the menin–MLL1 protein–protein interaction represents a promising strategy to block MLL1-mediated leukemogenesis. Employing a structure-based approach and starting from a linear MLL1 octapeptide, we have designed a class of potent macrocyclic peptidomimetic inhibitors of the menin–MLL1 interaction. The most potent macrocyclic peptidomimetic (MCP-1), 34, binds to menin with a Ki value of 4.7 nM and is >600 times more potent than the corresponding acyclic peptide. Compound 34 is also less peptide-like and has a lower molecular weight than the initial MLL1 peptide. Therefore, compound 34 serves as a promising lead structure for the design of potent and cell-permeable inhibitors of the menin–MLL1 interaction.

Our previously reported Bcl-2/Bcl-xL inhibitor, 4, effectively inhibited tumor growth but failed to achieve complete regression in vivo. We have now performed extensive modifications on its pyrrole core structure, which has culminated in the discovery of 32 (BM-1074). Compound 32 binds to Bcl-2 and Bcl-xL proteins with Ki values of <1 nM and inhibits cancer cell growth with IC50 values of 1–2 nM in four small-cell lung cancer cell lines sensitive to potent and specific Bcl-2/Bcl-xL inhibitors. Compound 32 is capable of achieving rapid, complete, and durable tumor regression in vivo at a well-tolerated dose schedule. Compound 32 is the most potent and efficacious Bcl-2/Bcl-xL inhibitor reported to date.

Mixed lineage leukemia 1 (MLL1) is a histone H3 lysine 4 (H3K4) methyltransferase, and targeting the MLL1 enzymatic activity has been proposed as a novel therapeutic strategy for the treatment of acute leukemia harboring MLL1 fusion proteins. The MLL1/WDR5 protein–protein interaction is essential for MLL1 enzymatic activity. In the present study, we designed a large number of peptidomimetics to target the MLL1/WDR5 interaction based upon −CO-ARA-NH–, the minimum binding motif derived from MLL1. Our study led to the design of high-affinity peptidomimetics, which bind to WDR5 with Ki < 1 nM and function as potent antagonists of MLL1 activity in a fully reconstituted in vitro H3K4 methyltransferase assay. Determination of co-crystal structures of two potent peptidomimetics in complex with WDR5 establishes their structural basis for high-affinity binding to WDR5. Evaluation of one such peptidomimetic, MM-102, in bone marrow cells transduced with MLL1-AF9 fusion construct shows that the compound effectively decreases the expression of HoxA9 and Meis-1, two critical MLL1 target genes in MLL1 fusion protein mediated leukemogenesis. MM-102 also specifically inhibits cell growth and induces apoptosis in leukemia cells harboring MLL1 fusion proteins. Our study provides the first proof-of-concept for the design of small-molecule inhibitors of the WDR5/MLL1 protein–protein interaction as a novel therapeutic approach for acute leukemia harboring MLL1 fusion proteins.

Nonpeptidic, bivalent Smac mimetics designed based upon monovalent Smac mimetics with a diazabicyclic core structure bind to XIAP, cIAP1, and cIAP2 with low to subnanomolar affinities and are highly effective in antagonizing XIAP in cell-free functional assays. They efficiently induce the degradation of cIAP1 and cIAP2 in cancer cells at concentrations as low as 1 nM, activate caspase-3 and -8, and cleave PARP at 3–10 nM. The most potent compounds in the series have IC50 of 3–5 nM in inhibition of cell growth in both MDA-MB-231and SK-OV-3 cell lines and are promising lead compounds for the development of a new class of cancer therapy.

Employing a structure-based strategy, we have designed a new class of potent small-molecule inhibitors of the anti-apoptotic proteins Bcl-2 and Bcl-xL. An initial lead compound with a new scaffold was designed based upon the crystal structure of Bcl-xL and U.S. Food and Drug Administration (FDA) approved drugs and was found to have an affinity of 100 μM for both Bcl-2 and Bcl-xL. Linking this weak lead to another weak-affinity fragment derived from Abbott’s ABT-737 led to an improvement of the binding affinity by a factor of >10 000. Further optimization ultimately yielded compounds with subnanomolar binding affinities for both Bcl-2 and Bcl-xL and potent cellular activity. The best compound (21) binds to Bcl-xL and Bcl-2 with Ki < 1 nM, inhibits cell growth in the H146 and H1417 small-cell lung cancer cell lines with IC50 values of 60–90 nM, and induces robust cell death in the H146 cancer cell line at 30–100 nM.

Bcl-2 and Bcl-xL antiapoptotic proteins are attractive cancer therapeutic targets. We have previously reported the design of 4,5-diphenyl-1H-pyrrole-3-carboxylic acids as a class of potent Bcl-2/Bcl-xL inhibitors. In the present study, we report our structure-based optimization for this class of compounds based upon the crystal structure of Bcl-xL complexed with a potent lead compound. Our efforts accumulated into the design of compound 30 (BM-957), which binds to Bcl-2 and Bcl-xL with Ki < 1 nM and has low nanomolar IC50 values in cell growth inhibition in cancer cell lines. Significantly, compound 30 achieves rapid, complete, and durable tumor regression in the H146 small-cell lung cancer xenograft model at a well-tolerated dose schedule.

Bcl-2 and Bcl-xL are key apoptosis regulators and attractive cancer therapeutic targets. We have designed and optimized a class of small-molecule inhibitors of Bcl-2 and Bcl-xL containing a 4,5-diphenyl-1H-pyrrole-3-carboxylic acid core structure. A 1.4 Å resolution crystal structure of a lead compound, 12, complexed with Bcl-xL has provided a basis for our optimization. The most potent compounds, 14 and 15, bind to Bcl-2 and Bcl-xL with subnanomolar Ki values and are potent antagonists of Bcl-2 and Bcl-xL in functional assays. Compounds 14 and 15 inhibit cell growth with low nanomolar IC50 values in multiple small-cell lung cancer cell lines and induce robust apoptosis in cancer cells at concentrations as low as 10 nM. Compound 14 also achieves strong antitumor activity in an animal model of human cancer.

The interaction between β-catenin and B-cell CLL/lymphoma 9 (BCL9), critical for the transcriptional activity of β-catenin, is mediated by a helical segment from BCL9 and a large binding groove in β-catenin. Design of potent, metabolically stable BCL9 peptides represents an attractive approach to inhibit the activity of β-catenin. In this study, we report the use of the Huisgen 1,3-dipolar cycloaddition reaction to generate triazole-stapled BCL9 α-helical peptides. The high efficiency and mild conditions of this “click” reaction combined with the ease of synthesis of the necessary unnatural amino acids allows for facile synthesis of triazole-stapled peptides. We have performed extensive optimization of this approach and identified the optimal combinations of azido and alkynyl linkers necessary for stapling BCL9 helices. The unsymmetrical nature of the triazole staple also allowed the synthesis of double-stapled BCL9 peptides, which show a marked increase in helical character and an improvement in binding affinity and metabolic stability relative to wild-type and linear BCL9 peptides. This study lays the foundation for further optimization of these triazole-stapled BCL9 peptides as potent, metabolically stable, and cell-permeable inhibitors to target the β-catenin and BCL9 interaction.

Although Bcl-xL and Mcl-1, two antideath Bcl-2 members, have similar, flexible binding sites, they can achieve high binding selectivity to endogenous binding partners and synthetic small-molecule inhibitors. Here, we employed molecular dynamic (MD) simulations and hotspot analysis to investigate the conformational flexibility of these proteins and their binding hotspots at the binding sites. Backbone flexibility analyses indicate that the highest degree of flexibility in Mcl-1 is the α4 helical segment as opposed to the α3 helix in Bcl-xL among four helical segments in their binding sites. Furthermore, common and unique binding hotspots at both proteins were identified using small-molecule probes. These analyses can aid the design of potent and specific small-molecule inhibitors for these proteins.Keywords: backbone flexibility; Bcl-xL; binding selectivity; cosolvent molecular dynamics simulation; Mcl-1

We have designed, synthesized and evaluated a series of new compounds with the goal to identify potent and selective D3 ligands. The two most potent and selective new D3 ligands are compounds 38 and 52, which bind to the D3 receptors with a Ki value of <1 nM and display a selectivity of 450–494 times over the D2 receptors and >10,000 times over the D1 receptors. Both 38 and 52 are full agonists with high potency at the D3 receptor in a D3 functional assay.

Apoptosis resistance is a hallmark of human cancer. Research in the last two decades has identified key regulators of apoptosis, including inhibitor of apoptosis proteins (IAPs). These critical apoptosis regulators have been targeted for the development of new cancer therapeutics. In this article, we will discuss three members of IAP proteins, namely XIAP, cIAP1 and cIAP2, as cancer therapeutic targets and the progress made in developing new cancer therapeutic agents to target these IAP proteins.

We report the discovery and characterization of SM-406 (compound 2), a potent and orally bioavailable Smac mimetic and an antagonist of the inhibitor of apoptosis proteins (IAPs). This compound binds to XIAP, cIAP1, and cIAP2 proteins with Ki of 66.4, 1.9, and 5.1 nM, respectively. Compound 2 effectively antagonizes XIAP BIR3 protein in a cell-free functional assay, induces rapid degradation of cellular cIAP1 protein, and inhibits cancer cell growth in various human cancer cell lines. It has good oral bioavailability in mice, rats, non-human primates, and dogs, is highly effective in induction of apoptosis in xenograft tumors, and is capable of complete inhibition of tumor growth. Compound 2 is currently in phase I clinical trials for the treatment of human cancer.

We have synthesized and evaluated a series of nonpeptidic, bivalent Smac mimetics as antagonists of the inhibitor of apoptosis proteins and new anticancer agents. All these bivalent Smac mimetics bind to full-length XIAP with low nanomolar affinities and function as ultrapotent antagonists of XIAP. While these Smac mimetics bind to cIAP1/2 with similar low nanomolar affinities, their potencies to induce degradation of cIAP1/2 proteins in cells differ by more than 100-fold. The most potent bivalent Smac mimetics inhibit cell growth with IC50 from 1 to 3 nM in the MDA-MB-231 breast cancer cell line and are 100 times more potent than the least potent compounds. Determination of intracellular concentrations for several representative compounds showed that the linkers in these bivalent Smac mimetics significantly affect their intracellular concentrations and hence the overall cellular activity. Compound 27 completely inhibits tumor growth in the MDA-MB-231 xenografts while causing no signs of toxicity in the animals.

We have identified several ligands with high binding affinities to the dopamine D3 receptor and excellent selectivity over the D2 and D1 receptors. CJ-1639 (17) binds to the D3 receptor with a Ki value of 0.50 nM and displays a selectivity of >5000 times over D2 and D1 receptors in binding assays using dopamine receptors expressed in the native rat brain tissues. CJ-1639 binds to human D3 receptor with a Ki value of 3.61 nM and displays over >1000-fold selectivity over human D1 and D2 receptors. CJ-1639 is active at 0.01 mg/kg at the dopamine D3 receptor in the rat and only starts to show a modest D2 activity at doses as high as 10 mg/kg. CJ-1639 is the most potent and selective D3 full agonist reported to date.Keywords: agonists; Dopamine receptors; drug abuse; ligands

Identifying binding hot spots in protein−protein interfaces is important for understanding the binding specificity and for the design of nonpeptide, small molecule inhibitors. Molecular dynamics simulation in the isopropanol/water cosolvent environment and in water was employed to investigate Bcl-xL protein, which has a highly flexible, large, and primarily hydrophobic binding site. Simulations of either the apo- or holocrystal structures of the Bcl-xL in pure water fail to generate conformations found in the cocrystal structures of Bcl-xL in complex with its binding partners due to hydrophobic collapse. In contrast, simulations in cosolvent starting either from the apo- or holocrystal structure of the Bcl-xL yield binding-site conformations similar to that found in the cocrystal structures of Bcl-xL. Hydrophobic binding hot spots identified using the conformations from the cosolvent simulations are in excellent agreement with experimental structural data of known inhibitors. Importantly, cosolvent simulations revealed the highly dynamic nature of the hydrophobic binding pockets in Bcl-xL and yielded new structural insights for the design of novel Bcl-xL small-molecule inhibitors.Keywords: Bcl-xL protein; cosolvent molecular dynamics simulation; Protein−protein interfaces

MLL1 is a histone 3 lysine 4 (H3K4) methyltransferase and a promising new cancer therapeutic target. The catalytic activity of MLL1 is regulated by the formation of a core complex consisting of MLL1, WDR5, RbBP5, and Ash2L. The interaction between WDR5 and MLL1 plays an essential role in regulation of the H3K4 methyltransferase activity of MLL1 and targeting this interaction using small molecules may represent an attractive therapeutic strategy. In this study, we have defined the essential elements in MLL1 required for its high-affinity binding to WDR5. Our data showed that the minimal elements crucial for high-affinity binding of MLL1 to WDR5 are −CO-ARA-NH− motif and two intramolecular hydrogen bonds that stabilize the conformation of this motif. Two 3-mer peptides, Ac-ARA-NH2 and Ac-ART-NH2, were designed based upon MLL1 and H3 sequences and achieved Ki values of 120 and 20 nM to WDR5, respectively. Our study provides a concrete basis for the design of potent peptidomimetics and nonpeptidic compounds to inhibit MLL1 activity by targeting the MLL1 and WDR5 interaction.

A series of compounds were designed and synthesized as antagonists of cIAP-1/2 and XIAP based upon our previously identified lead compound SM-122 (1). The most potent of these (7) binds to XIAP, cIAP-1, and cIAP-2 proteins with Ki values of 36, <1, and <1.9 nM, respectively. Consistent with its potent binding affinities to IAPs, 7 effectively antagonizes XIAP in a cell-free caspase-9 functional assay, efficiently induces cIAP-1 degradation in cells at concentrations as low as 10 nM, and triggers activation of caspases and PARP cleavage in the MDA-MB-231 breast cancer cell line. Compound 7 potently inhibits cell growth in the MDA-MB-231 cancer cell line with an IC50 value of 200 nM and is 9 times more potent than compound 1.

We report herein the structure-based design of a class of conformationally constrained, potent, cell-permeable small-molecule inhibitors to target the SH2 domain in STAT3. Compound 11 (CJ-1383) binds to STAT3 with a Ki value of 0.95 μM, dose-dependently inhibits cellular STAT3 signaling and cancer cell growth, and induces apoptosis in the MDA-MB-468 cancer cell line with constitutively activated STAT3.Keywords: apoptosis; SH2 domain; STAT3 inhibitor

Mapping protein hotspots and analysis of the binding free energy associated with each hotspot can provide critical information for drug design. In the present study, we have performed computational analysis for the two known hotspots in thermolysin. Our data showed that the free energy double-decoupling method can determine the binding free energy of different probe molecules associated with the same hotspot or different hotspots with the same probe molecule. The less expensive cosolvent mapping method can be used to readily identify known protein hotspots without prior knowledge and also provide a good estimate of the binding free energy, as compared to the more expensive free energy double-decoupling method. Hence, the combination of the cosolvent mapping method to identify potential protein hotspots followed by more rigorous calculation of the binding free energy associated with each hotspot using the double-decoupling method can provide very useful information for drug design.Keywords: binding free energy; Computational analysis; cosolvent mapping method; double-decoupling method; protein hotspots

Two cyclopeptidic Smac mimetics, 2 and 3, were designed and synthesized. These two compounds bind to XIAP and cIAP-1/2 with low nanomolar affinities, and restore the activities of caspase-9 and caspase-3/-7 inhibited by XIAP. Compound 2 potently inhibits cancer cell growth and is 5–8 times more potent than the initial lead compound.

Accurate prediction of the binding affinities of small-molecule ligands to their biological targets is fundamental for structure-based drug design but remains a very challenging task. In this paper, we have performed computational studies to predict the binding models of 31 small-molecule Smac (the second mitochondria-derived activator of caspase) mimetics to their target, the XIAP (X-linked inhibitor of apoptosis) protein, and their binding affinities. Our results showed that computational docking was able to reliably predict the binding models, as confirmed by experimentally determined crystal structures of some Smac mimetics complexed with XIAP. However, all the computational methods we have tested, including an empirical scoring function, two knowledge-based scoring functions, and MM-GBSA (molecular mechanics and generalized Born surface area), yield poor to modest prediction for binding affinities. The linear correlation coefficient (r2) value between the predicted affinities and the experimentally determined affinities was found to be between 0.21 and 0.36. Inclusion of ensemble protein−ligand conformations obtained from molecular dynamic simulations did not significantly improve the prediction. However, major improvement was achieved when the free-energy change for ligands between their free- and bound-states, or “ligand-reorganization free energy”, was included in the MM-GBSA calculation, and the r2 value increased from 0.36 to 0.66. The prediction was validated using 10 additional Smac mimetics designed and evaluated by an independent group. This study demonstrates that ligand reorganization free energy plays an important role in the overall binding free energy between Smac mimetics and XIAP. This term should be evaluated for other ligand−protein systems and included in the development of new scoring functions. To our best knowledge, this is the first computational study to demonstrate the importance of ligand reorganization free energy for the prediction of protein−ligand binding free energy.

We report herein the design of potent and orally active small-molecule inhibitors of the MDM2−p53 interaction. Compound 5 binds to MDM2 with a Ki of 0.6 nM, activates p53 at concentrations as low as 40 nM, and potently and selectively inhibits cell growth in tumor cells with wild-type p53 over tumor cells with mutated/deleted p53. Compound 5 has a good oral bioavailability and effectively inhibits tumor growth in the SJSA-1 xenograft model.

A series of new Smac mimetics have been designed, synthesized, and evaluated. The most potent compound 10 binds to XIAP, cIAP-1, and cIAP-2 BIR3 proteins with Ki of 3.9, 0.37, and 0.25 nM, respectively. Compound 10 antagonizes XIAP in a cell-free functional assay and induces rapid cIAP-1 degradation in cancer cells. Compound 10 inhibits cell growth in the MDA-MB-231 cancer cell line with an IC50 of 8.9 nM.

The transcriptional activator β-catenin is the primary mediator of the canonical Wnt signaling pathway and is frequently upregulated in many types of human cancer. Recent studies have suggested that the interaction of β-catenin and its cofactor, B-cell lymphoma 9 (BCL9), is crucial for its transcriptional activity. Targeting this interaction using small molecules will improve our understanding of the β-catenin/Wnt signaling pathway and may lead to the development of a new class of anticancer drugs. In this study, we developed a fluorescence polarization (FP)-based BCL9 binding assay. Using our initial FP assay, we performed extensive mutational analysis on four critical hydrophobic residues in the BCL9 peptide and determined the precise region in BCL9 responsible for binding to β-catenin. These results led to further optimization of our FP assay, making it amenable for high-throughput screening (HTS). We also developed and validated a complementary surface plasmon resonance (SPR)-based binding assay and showed that our synthetic BCL9-based peptides are capable of fully inhibiting the binding of β-catenin to wild-type BCL9 protein. Our studies provide not only further insight into the interaction between BCL9 and β-catenin but also quantitative and reliable biochemical binding assays for the discovery of potent and specific small-molecule inhibitors of this interaction.

The STAT3 oncogene is a promising molecular target for the design of a new class of anticancer drugs. In this letter, we describe the design, synthesis, and evaluation of peptidomimetics containing Freidinger lactams as novel STAT3 inhibitors. Compound 3 binds to STAT3 with a Ki value of 190 nM and is a promising lead compound for further design and optimization.

Smac/DIABLO is a protein released from mitochondria into the cytosol in response to apoptotic stimuli. Smac promotes apoptosis at least in part through antagonizing inhibitor of apoptosis proteins (IAPs), including XIAP, cIAP-1, and cIAP-2. Smac interacts with these IAPs via its N-terminal AVPI binding motif. There has been an enormous interest in academic laboratories and pharmaceutical companies in the design of small-molecule Smac mimetics as potential anticancer agents. This task is particularly challenging because it involves targeting protein−protein interactions. Nevertheless, intense research has now generated potent, specific, cell-permeable small-molecule peptidomimetics and nonpeptidic mimetics. To date, two types of Smac mimetics have been reported, namely, monovalent and bivalent Smac mimetics. The monovalent compounds are designed to mimic the binding of a single AVPI binding motif to IAP proteins, whereas the bivalent compounds contain two AVPI binding motif mimetics tethered together through a linker. Studies from several groups have clearly demonstrated that both monovalent and bivalent Smac mimetics not only enhance the antitumor activity of other anticancer agents but also can induce apoptosis as single agents in a subset of human cancer cell lines in vitro and are capable of achieving tumor regression in animal models of human cancer. In general, bivalent Smac mimetics are 100−1000 times more potent than their corresponding monovalent Smac mimetics in induction of apoptosis in tumor cells. However, properly designed monovalent Smac mimetics can achieve oral bioavailability and may have major advantages over bivalent Smac mimetics as potential drug candidates. In-depth insights on the molecular mechanism of action of Smac mimetics have been provided by several independent studies. It was shown that Smac mimetics induce apoptosis in tumor cells by targeting cIAP-1/-2 for the rapid degradation of these proteins, which leads to activation of nuclear factor κB (NF-κB) and production and secretion of tumor necrosis factor α (TNFα). TNFα promotes formation of a receptor-interacting serine−threonine kinase 1 (RIPK1)-dependent caspase-8-activating complex, leading to activation of caspase-8 and -3/-7 and ultimately to apoptosis. For the most efficient apoptosis induction, Smac mimetics also need to remove the inhibition of XIAP to caspase-3/-7. Hence, Smac mimetics induce apoptosis in tumor cells by targeting not only cIAP-1/-2 but also XIAP. The employment of potent, cell-permeable, small-molecule Smac mimetics has yielded important insights into the regulation of apoptosis by IAP proteins. To date, at least one Smac mimetic has been advanced into clinical development. Several other Smac mimetics are in an advanced preclinical development stage and are expected to enter human clinical testing for the treatment of cancer in the near future.

A series of compounds structurally related to pramipexole were designed, synthesized, and evaluated as ligands for the dopamine 3 (D3) receptor. Compound 12 has a Ki value of 0.41 nM to D3 and a selectivity of >30000- and 800-fold over the D1-like and D2 receptors, respectively. Our in vivo functional assays showed that this compound is a partial agonist at the D3 receptor with no detectable activity at the D2 receptor.

A series of acylpyrogallols were designed, synthesized, and evaluated as small-molecule inhibitors of antiapoptotic Bcl-2 proteins. The most potent compound 9 (TM-179) binds to Bcl-2 with an IC50 of 170 nM and to Mcl-1 with a Ki of 37 nM. Compound 9 potently inhibits cell growth and induces apoptosis in human breast and prostate cancer cell lines.

Small molecules designed to mimic the binding of Smac protein to X-linked inhibitor of apoptosis protein (XIAP) are being pursued as a promising new class of anticancer drugs. Herein, we report the design, synthesis, and comprehensive structure−activity relationship studies of a series of conformationally constrained bicyclic Smac mimetics. Our studies led to the discovery of a number of highly potent and cell-permeable Smac mimetics and yielded important new insights into their structure−activity relationship for their binding to XIAP and for their activity in inhibition of cancer cell growth. Determination of the crystal structure of one potent Smac mimetic, compound 21, in complex with XIAP BIR3 provides the structural basis for its high-affinity binding to XIAP and for the design of highly potent Smac mimetics.

A series of tricyclic, conformationally constrained Smac mimetics have been designed, synthesized, and evaluated. The most potent compound 6 (WS-5) binds to XIAP, cIAP-1, and cIAP-2 with Ki of 18, 1.1, and 4.2 nM, respectively. Compound 6 antagonizes XIAP in a functional assay, induces cIAP-1 degradation, inhibits cell growth with an IC50 of 68 nM in the MDA-MB-231 cancer cell line, and effectively induces cancer cells to undergo apoptosis.

We have designed and synthesized a cyclic, bivalent Smac mimetic (compound 3) and characterized its interaction with the X-linked inhibitor of apoptosis protein (XIAP). Compound 3 binds to XIAP containing both BIR2 and BIR3 domains with a biphasic dose−response curve representing two binding sites with IC50 values of 0.5 and 406 nM, respectively. Compound 3 binds to XIAPs containing the BIR3-only and BIR2-only domain with Ki values of 4 nM and 4.4 μM, respectively. Gel filtration experiments using wild-type and mutated XIAPs showed that 3 forms a 1:2 stoichiometric complex with XIAP containing the BIR3-only domain. However, it forms a 1:1 stoichiometric complex with XIAP containing both BIR2 and BIR3 domains, and both BIR domains are involved in the binding. Compound 3 efficiently antagonizes inhibition of XIAP in a cell-free functional assay and is >200 times more potent than its corresponding monovalent compound 2. Determination of the crystal structure of 3 in complex with the XIAP BIR3 domain confirms that 3 induces homodimerization of the XIAP BIR3 domain and provides a structural basis for the cooperative binding of one molecule of compound 3 to two XIAP BIR3 molecules. On the basis of this crystal structure, a binding model of XIAP containing both BIR2 and BIR3 domains and 3 was constructed, which sheds light on the ability of 3 to relieve the inhibition of XIAP with not only caspase-9 but also caspase-3/-7. Compound 3 is cell-permeable, effectively activates caspases in whole cells, and potently inhibits cancer cell growth. Compound 3 is a useful biochemical and pharmacological tool for further elucidating the role of XIAP in regulation of apoptosis and represents a promising lead compound for the design of potent, cell-permeable Smac mimetics for cancer treatment.

XIAP (X-chromosome-linked inhibitor of apoptosis protein) is an inhibitor of apoptosis by binding to and inhibition of caspase-3 and caspase-7 through its BIR2 domain and caspase-9 through its BIR3 domain. Smac (second mitochondria-derived activator of caspases) protein is an endogenous antagonist of XIAP. Smac forms a dimer and concurrently binds both the BIR2 and BIR3 domains in XIAP, functioning as a highly efficient and potent cellular inhibitor of XIAP. In this article, we have designed and synthesized a bivalent Smac-based ligand (Smac-1) and its fluorescent labeled analogue (Smac-1F) and characterized their interaction with different constructs of XIAP. Our study demonstrates that bivalent Smac-based ligands bind concurrently to both the BIR2 and BIR3 domains of XIAP and are more than 500 times more potent than the corresponding monovalent Smac-based ligands. Bivalent Smac-based ligands also function as much more potent antagonists of XIAP than do the corresponding monovalent Smac-based ligands in cell-free functional assays. Using Smac-1F and XIAP containing both BIR2 and BIR3 domains, we also developed and validated a new fluorescence polarization-based assay. Hence, our designed bivalent Smac-based peptides mimic the mode of dimeric Smac protein in their interaction with XIAP containing both BIR2 and BIR3 domains and achieve extremely high potency in binding and functional assays. Our study provides new insights into the mode of action of bivalent Smac ligands targeting XIAP and a basis for the design and development of cell-permeable, bivalent Smac mimetics.

We have designed MI-219 as a potent, highly selective and orally active small-molecule inhibitor of the MDM2–p53 interaction. MI-219 binds to human MDM2 with a K i value of 5 nM and is 10,000-fold selective for MDM2 over MDMX. It disrupts the MDM2–p53 interaction and activates the p53 pathway in cells with wild-type p53, which leads to induction of cell cycle arrest in all cells and selective apoptosis in tumor cells. MI-219 stimulates rapid but transient p53 activation in established tumor xenograft tissues, resulting in inhibition of cell proliferation, induction of apoptosis, and complete tumor growth inhibition. MI-219 activates p53 in normal tissues with minimal p53 accumulation and is not toxic to animals. MI-219 warrants clinical investigation as a new agent for cancer treatment.

A series of small-molecule Smac mimetics containing a diazabicyclic core structure have been designed, synthesized, and evaluated. The most potent compound (6) binds to XIAP, cIAP-1, and cIAP-2 with Ki values of 8.4, 1.5, and 4.2 nM, respectively, directly antagonizes XIAP in a cell-free functional assay and induces cIAP-1 degradation in cancer cells. It inhibits cell growth with an IC50 value of 31 nM, effectively induces apoptosis in the MDA-MB-231 cancer cell line, and has a good oral bioavailability.

STAT3 is a promising molecular target for the design of new anticancer drugs. In this paper, we report the design and synthesis of a conformationally constrained macrocyclic peptidomimetic 2 via click chemistry. Compound 2 was determined to bind to STAT3 with a Ki value of 7.3 μM in a competitive fluorescence-polarization-based binding assay, representing a promising initial lead compound for further optimization.

We have recently reported hexahydropyrazinoquinolines as a new class of dopamine 3 (D3) receptor ligands with high-affinity to the D3 receptor and excellent selectivity over the closely related D1-like and D2-like receptors. However, our previously reported most potent and selective D3 ligands have poor aqueous solubility, which greatly hinders our in vivo studies aimed at evaluation of their therapeutic potential in animal models. In this study, we wish to report the design, synthesis, and evaluation of a series of new hexahydropyrazinoquinolines as D3 ligands with improved solubility. Among them, compound 4g has a Ki value of 9.7 nM for the D3 receptor and displays a selectivity of >5000 and 466 times over the D1-like and D2-like receptors, respectively. Importantly, the hydrochloride salt form of compound 4g has a good aqueous solubility (>50 mg/mL) and represents a promising D3 ligand for further in vivo evaluations of its therapeutic potential for the treatment of drug abuse, restless legs syndrome, schizophrenia, Parkinson’s disease, and depression.Ki = 9.7 nM to the D3 receptor Selectivities of >5000 and 466 times over the D1-like and D2-like receptors.

Structure-based design, chemical synthesis and biochemical testing of a series of novel Smac peptido-mimetics as inhibitors of XIAP protein are described. The most potent compound, 6j, has a binding affinity (Ki value) of 24 nM to XIAP BIR3 protein and is 24 times more potent than the native Smac AVPI peptide. Further optimization of these potent Smac mimetics may ultimately lead to the development of a novel class of anticancer drugs for the treatment of human cancer by overcoming apoptosis-resistance of cancer cells through targeting the inhibitor of apoptosis proteins.

A hexahydropyrazinoquinoline (compound 5c) was previously discovered as a novel D3 ligand with a moderate binding affinity to the D3 receptor (Ki = 304 nM) but no selectivity over the D1-like and D2-like receptors. In this study, we wish to report the design, synthesis and structure–activity relationship studies of a series of novel hexahydropyrazinoquinolines. Our efforts resulted in new compounds with improved binding affinity and selectivity. Among them, compound 12d has a Ki value of 2.6 nM for its binding affinity to the D3 receptor and has >2000- and 99-fold selectivity over the D1-like and D2-like receptors, respectively, representing a potent and selective D3 ligand.

The X-linked inhibitor of apoptosis protein (XIAP) is a potent cellular inhibitor of apoptosis. Designing small-molecule inhibitors that target the BIR3 domain of XIAP, where Smac/DIABLO (second mitochondria-derived activator of caspase/direct IAP-binding protein with low pI) and caspase-9 bind, is a promising strategy for inhibiting the antiapoptotic activity of XIAP and for overcoming apoptosis resistance of cancer cells mediated by XIAP. Herein, we report the development of a homogeneous high-throughput assay based on fluorescence polarization for measuring the binding affinities of small-molecule inhibitors to the BIR3 domain of XIAP. Among four fluorescent probes tested, a mutated N-terminal Smac peptide (AbuRPFK-(5-Fam)-NH2) showed the highest affinity (Kd = 17.92 nM) and a large dynamic range (ΔmP=231±0.9), and was selected as the most suitable probe for the binding assay. The binding conditions (DMSO tolerance and stability) have been investigated. Under optimized conditions, a Z′ factor of 0.88 was achieved in a 96-well format for high-throughput screening. It was found that the popular Cheng–Prusoff equation is invalid for the calculation of the competitive inhibition constants (Ki values) for inhibitors in the FP-based competitive binding assay conditions, and accordingly, a new mathematical equation was developed, validated, and used to compute the Ki values. An associated Web-based computer program was also developed for this task. Several known Smac peptides with high and low affinities have been evaluated under the assay conditions and the results obtained indicated that the FP-based competitive binding assay performs correctly as designed: it can quantitatively and accurately determine the binding affinities of Smac-based peptide inhibitors with a wide range of affinities, and is suitable for high-throughput screening of inhibitors binding to the XIAP BIR3 domain.

We previously identified hexahydrobenz[f]isoquinoline (4a) as a new class of dopamine 3 receptor (D3) ligand. Herein, we described the design, synthesis, and preliminary structure–activity relationships of new analogues of 4a as a novel class of D3 ligands. Among these new analogues, compound 4h is a potent D3 ligand (Ki = 6.1 nM) and has a selectivity of 133-fold between D3- and D2-like receptors, and of 163-fold between D3- and D1-like receptors, respectively. Thus, compound 4h represents a promising new lead compound for further design and optimization toward achieving highly potent and selective D3 ligands.

There is considerable interest in developing dopamine transporter (DAT) inhibitors as potential therapies for the treatment of cocaine abuse. We report herein our pharmacophore-based discovery and molecular modeling-assisted rational design of 2,3-disubstituted quinuclidines as potent DAT inhibitors with a novel chemical scaffold. Through 3-D-database pharmacophore searching, compound 12 was identified as a very weak DAT inhibitor with Ki values of 7.3 and 8.9 μM in [3H]mazindol binding and in inhibition of dopamine reuptake, respectively. Molecular modeling-assisted rational design and chemical modifications led to identification of potent analogues (−)-29 and 34 with Ki values of 14 and 32 nM for both compounds in binding affinity and inhibition of dopamine reuptake, respectively. Behavioral pharmacological evaluations in rodents showed that 34 has a profile very different from cocaine. While 34 is substantially more potent than cocaine as a DAT inhibitor, it is approximately four times less potent than cocaine in mimicking the discriminative stimulus properties of cocaine in rat. On the other hand, 34 (3–30 mg/kg) lacks either the locomotor stimulant or stereotypic properties of cocaine in mice. Importantly, 34 blocks locomotor stimulant activity induced by 20 mg/kg cocaine in mice, with an estimated ED50 of 19 mg/kg. Taken together, our data suggest that 34 represents a class of potent DAT inhibitors with a novel chemical scaffold and a behavioral pharmacological profile different from that of cocaine in rodents. Thus, 34 may serve as a novel lead compound in the ultimate development of therapeutic entities for cocaine abuse and/or addiction.Graphic

Abnormal dopamine signaling in brain has been implicated in several conditions such as cocaine abuse, Parkinson's disease and depression. Potent and selective dopamine transporter inhibitors may be useful as pharmacological tools and therapeutic agents. Simple substituted pyridines were discovered as novel dopamine transporter (DAT) inhibitors through pharmacophore-based 3D-database search. The most potent compound 18 has a Ki value of 79 nM in inhibition of WIN35,248 binding to dopamine transporter and 255 nM in inhibition of dopamine reuptake, respectively, as potent as cocaine. Preliminary structure–activity relationship studies show that the geometry and the nature of the substituents on the pyridine ring determine the inhibitory activity and selectivity toward the three monoamine transporters. The substituted pyridines described herein represent a class of novel DAT inhibitors with simple chemical structures and their discovery provides additional insights into the binding site of DAT.The discovery of novel dopamine transporter inhibitors using a new pharmacophore model through 3D-database pharmacophore searching is described. A simple substituted pyridine has a Ki value of 79 nM in inhibition of dopamine reuptake.

Substituted 3,4-diphenyl-1,3-thiazols were identified as a class of novel and potent monoamine transporter inhibitors through a 3-D pharmacophore search using a new pharmacophore model derived from mazindol. The most potent compound (13) has Ki values of 24 and 23 nM in binding to dopamine transporter and inhibition of dopamine reuptake, respectively.3,4-Diphenyl-thiazoles were identified as a novel class of monoamine transporter inhibitors (Ki=24 nM at DAT).

Apoptosis is a tightly regulated cellular process and faulty regulation of apoptosis is a hallmark of human cancers. Targeting key apoptosis regulators with the goal to restore apoptosis in tumor cells has been pursued as a new cancer therapeutic strategy. XIAP, cIAP1, and cIAP2, members of inhibitor of apoptosis (IAP) proteins, are critical regulators of cell death and survival and are attractive targets for new cancer therapy. The SMAC/DIABLO protein is an endogenous antagonist of XIAP, cIAP1, and cIAP2. In the last decade, intense research efforts have resulted in the design and development of several small-molecule SMAC mimetics now in clinical trials for cancer treatment. In this review, we will discuss the roles of XIAP, cIAP1, and cIAP2 in regulation of cell death and survival, and the design and development of small-molecule SMAC mimetics as novel cancer treatments.

Crizotinib is the first anaplastic lymphoma kinase (ALK) inhibitor to have been approved for the treatment of non–small cell lung cancer (NSCLC) harboring an ALK fusion gene, but it has been found that, in the clinic, patients develop resistance to it. Alectinib and ceritinib are second-generation ALK inhibitors which show remarkable clinical responses in both crizotinib-naive and crizotinib-resistant NSCLC patients harboring an ALK fusion gene. Despite their impressive activity, clinical resistance to alectinib and ceritinib has also emerged. In the current study, we elucidated the resistance mechanisms to these second-generation ALK inhibitors in the H3122 NSCLC cell line harboring the EML4-ALK variant 1 fusion in vitro. Prolonged treatment of the parental H3122 cells with alectinib and ceritinib led to two cell lines which are 10 times less sensitive to alectinib and ceritinib than the parental H3122 cell line. Although mutations of ALK in its kinase domain are a common resistance mechanism for crizotinib, we did not detect any ALK mutation in these resistant cell lines. Rather, overexpression of phospho-ALK and alternative receptor tyrosine kinases such as phospho-EGFR, phospho-HER3, and phospho-IGFR-1R was observed in both resistant cell lines. Additionally, NRG1, a ligand for HER3, is upregulated and responsible for resistance by activating the EGFR family pathways through the NRG1-HER3-EGFR axis. Combination treatment with EGFR inhibitors, in particular afatinib, was shown to be effective at overcoming resistance. Our study provides new mechanistic insights into adaptive resistance to second-generation ALK inhibitors and suggests a potential clinical strategy to combat resistance to these second-generation ALK inhibitors in NSCLC.

•MM-401 inhibits MLL1 H3K4 methylation without affecting other MLL family members•MM-401 inhibits MLL cells, but not normal BM or non-MLL cells•RNA-seq analyses show correlative changes upon MM-401 treatment and MLL1 deletion•Targeting of MLL1 activity has therapeutic potential for MLLHere we report a comprehensive characterization of our recently developed inhibitor MM-401 that targets the MLL1 H3K4 methyltransferase activity. MM-401 is able to specifically inhibit MLL1 activity by blocking MLL1-WDR5 interaction and thus the complex assembly. This targeting strategy does not affect other mixed-lineage leukemia (MLL) family histone methyltransferases (HMTs), revealing a unique regulatory feature for the MLL1 complex. Using MM-401 and its enantiomer control MM-NC-401, we show that inhibiting MLL1 methyltransferase activity specifically blocks proliferation of MLL cells by inducing cell-cycle arrest, apoptosis, and myeloid differentiation without general toxicity to normal bone marrow cells or non-MLL cells. More importantly, transcriptome analyses show that MM-401 induces changes in gene expression similar to those of MLL1 deletion, supporting a predominant role of MLL1 activity in regulating MLL1-dependent leukemia transcription program. We envision broad applications for MM-401 in basic and translational research.Download high-res image (112KB)Download full-size image

We have designed, synthesized, and evaluated a series of new compounds based upon our previously reported bivalent Smac mimetics. This led to the identification of compound 12 (SM-1200), which binds to XIAP, cIAP1, and cIAP2 with Ki values of 0.5, 3.7, and 5.4 nM, respectively, inhibits cell growth in the MDA-MB-231 breast cancer and SK-OV-3 ovarian cancer cell lines with IC50 values of 11.0 and 28.2 nM, respectively. Compound 12 has a much improved pharmacokinetic profile over our previously reported bivalent Smac mimetics and is highly effective in induction of rapid and durable tumor regression in the MDA-MB-231 xenograft model. These data indicate that compound 12 is a promising Smac mimetic and warrants extensive evaluation as a potential candidate for clinical development.

We report a class of potent and selective dopamine D3 receptor antagonists based upon tranylcypromine. Although tranylcypromine has a low affinity for the rat D3 receptor (Ki = 12.8 μM), our efforts have yielded (1R,2S)-11 (CJ-1882), which has Ki values of 2.7 and 2.8 nM at the rat and human dopamine D3 receptors, respectively, and displays respective selectivities of >10000-fold and 223-fold over the rat and human D2 receptors. Evaluation in a β-arrestin functional assay showed that (1R,2S)-11 is a potent and competitive antagonist at the human D3 receptor.