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Transthyretin (TTR) has a well-established role in neuroprotection in Alzheimer's Disease (AD). We have setup a drug discovery program of small-molecule compounds that act as chaperones enhancing TTR/Amyloid-beta peptide (Aβ) interactions. A combination of computational drug repurposing approaches and in vitro biological assays have resulted in a set of molecules which were then screened with our in-house validated high-throughput screening ternary test. A prioritized list of chaperones was obtained and corroborated with ITC studies. Small-molecule chaperones have been discovered, among them our lead compound Iododiflunisal (IDIF), a molecule in the discovery phase; one investigational drug (luteolin); and 3 marketed drugs (sulindac, olsalazine and flufenamic), which could be directly repurposed or repositioned for clinical use. Not all TTR tetramer stabilizers behave as chaperones in vitro. These chemically diverse chaperones will be used for validating TTR as a target in vivo, and to select one repurposed drug as a candidate to enter clinical trials as AD disease-modifying drug., I. Cardoso works under the Investigator FCT Program which is financed by national funds through FCT and co-financed by ESF through HPOP, type 4.2 - Promotion of Scientific Employment. M. Alemi was a recipient of a Research Fellowship (BIM) funded by the project of Fundació La Marató de TV3 (Spain), and L. M. Santos was a recipient of a fellowship from Norte 2020. J.P. Leite acknowledges the FCT fellowship SFRH/BD/129921/2017 (Portugal). IQAC-CSIC acknowledges a contract to Ellen Y. Cotrina funded by the project of Fundació Marató de TV3 (Spain) and a contract from Ford España - Fundación Apadrina la Ciencia (Spain). The group at CIC bioGUNE also acknowledges MINECO (Spain) for funding through grant CTQ2015-64597-C2-1-P and a Juan de la Cierva contract to A. Gimeno. We thank access to ALBA (XALOC), ESRF (ID30B) and Soleil (PROXIMA 1 and 2a) synchrotrons.

In the past few years, attempts have been made to use decision criteria beyond Lipinski’s guidelines (Rule of five) to guide drug discovery projects more effectively. Several variables and formulations have been proposed and investigated within the framework of multiparameter optimization methods to guide drug discovery. In this context, the combination of Ligand Efficiency Indices (LEI) has been predominantly used to map and monitor the drug discovery process in a retrospective fashion. Here we provide an example of the use of a novel application of the LEI methodology for prospective lead optimization by using the transthyretin (TTR) fibrillogenesis inhibitor iododiflunisal (IDIF) as example. Using this approach, a number of compounds with theoretical efficiencies higher than the reference compound IDIF were identified. From this group, ten compounds were selected, synthesized and biologically tested. Half of the compounds (5, 6, 7, 8 and 10) showed potencies in terms of IC50 inhibition of TTR aggregation equal or higher than the lead compound. These optimized compounds mapped within the region of more efficient candidates in the corresponding experimental nBEI-NSEI plot, matching their position in the theoretical optimization plane that was used for the prediction. Due to their upstream (North-Eastern) position in the progression lines of NPOL = 3 or 4 of the nBEI-NSEI plot, three of them (5, 6 and 8) are more interesting candidates than iododiflunisal because they have been optimized in the three crucial LEI variables of potency, size and polarity at the same time. This is the first example of the effectiveness of using the combined LEIs within the decision process to validate the application of the LEI formulation for the prospective optimization of lead compounds., We thank Dr. Lluís Bosch for help on the synthesis work. Funding Sources. This work was supported by a Grant 080530/31/32 from the Fundació Marató de TV3, Barcelona, Spain (to G.A, A.P., and J.Q.) and a Grant from Plan Nacional, Ministerio de Economía y Competitividad (Ref: CTQ2010-20517-C02-02) to G.A.

1,4-Dihydropyridines are well-known calcium channel blockers, but variations in the substituents attached to the ring have resulted in their role reversal making them calcium channel activators in some cases. We describe the microwave-assisted eco-friendly approach for the synthesis of pyranopyrazole-1,4-dihydropyridines, a new class of 1,4-DHPs, under solvent-free conditions in good yield, and screen them for various in silico, in vitro and in vivo activities. The in vivo experimentation results show that the compounds possess positive inotropic effect, and the docking results validate their good binding with calcium channels. Compounds 7c, 7g and 7i appear to be the most effective positive inotropes, even at low doses, and bind with the calcium channels even more strongly than Bay K 8644, a well-known calcium channel activator. The chronotropic effect for the new compounds was also studied. The target and off-target affinity profiling supported the in vivo results and revealed that the hybridized pyranopyrazole dihydropyridine scaffold has delivered new moderate hits, to be optimized, for the cytochrome P450 3A4 enzymes, opening avenues for combined pharmacological activity through standard structural modification.

The multifunctional character of tryptophan has made it a target for the development of new molecules with therapeutic applications. In this sense the design of alternative solid phase routes would allow the widening of synthetic possibilities to access these molecules through conventional or combinatorial strategies. The present work describes a new strategy for side-chain anchoring of tryptophan to dihydropyranyl-functionalized polystyrene resins and its application to the synthesis of the natural diketopiperazine Brevianamide F. For this study a new handle (4-[(3,4-dihydro-2H-pyran-2-yl)methoxy]benzoic acid) was prepared in order to functionalize aminomethyl or methylbenzhydrylamine resins. A preliminary study in solution using Fmoc-Trp-OR (R = Allyl or Me) and suitable resin models showed that the formation of an hemiaminal linkage with the indole system could be brought about by either conventional or microwave heating in 1,2-dichloroethane and in the presence of pyridine p-toluenesulfonate in yields of 70–95% practically without the formation of sub-products. On the other hand the amino acid could be liberated from the resin at room temperature in yields of up to 90% using trifluoroacetic acid in dichloromethane in the presence of 1,3-dimethoxybenzene as a cation scavenger. The conditions found in solution for the reversible formation of the hemiaminal were only reproducible in solid-phase work using conventional heating. These conditions were used in the synthesis of Brevianamide F, furnishing the diketopiperazine in an overall yield of 56%. These results demonstrate the potential of this strategy for the preparation of new molecules based upon tryptophan as a synthetic precursor.

The concept of ligand efficiency and the usage of ligand efficiency values to assess the quality of fragments and compounds is becoming more accepted in the practice of medicinal chemistry. This is particularly true as it refers to the efficiency of ligands per unit size (i.e., binding affinity/number of non-hydrogen atoms or binding affinity/MW). The use of the Ligand Efficiency Indices (LEIs) as variables for a Cartesian mapping of chemico-biological space, the concept of AtlasCBS, has been presented in a recent publication with some initial drug-discovery applications. In this communication, we present additional applications of the concept in three domains of drug discovery: i) analyze and compare the content of databases: inhibitors vs. drugs; ii) polypharmacology; and iii) applications to Fragment-Based strategies. We suggest that the combined use of LEIs in a Cartesian representation of Chemico-Biological Space (AtlasCBS) could be a useful tool in various aspects of drug-discovery in the future.

We have previously reported the design and synthesis of ligands that stabilize Transthyretin protein (TTR) in order to obtain therapeutically active compounds for Familial Amyloid Polyneuropathy (FAP). We are hereby reporting a drug design strategy to optimize these ligands and map them in Chemico-Biological Space (CBS) using Ligand Efficiency Indices (LEIs). We use a binding efficiency index (BEI) based on the measured binding affinity related to the molecular weight (MW) of the compound combined with surface-binding efficiency index (SEI) based on Polar Surface Area (PSA). We will illustrate the use of these indices, combining three crucial variables (potency, MW and PSA) in a 2D graphical representation of chemical space, to perform a retrospective mapping of SAR data for a current TTR inhibitors database, and we propose prospective strategies to use these efficiency indices and chemico-biological space maps for optimization and drug design efforts for TTR ligands., This work was supported by a grant from the Fundaci Marat de TV3, Barcelona, Spain (Project Number: 080530/ 31/32).