Fragment-based lead discovery is becoming an increasingly popular strategy for drug discovery. Fragment screening identifies weakly binding compounds that require optimization to become high-affinity leads. As design of leads from fragments is challenging, reliable computational methods to guide optimization would be invaluable. We evaluated using molecular dynamics simulations and the free energy perturbation method (MD/FEP) in fragment optimization for the A2A adenosine receptor, a pharmaceutically relevant G protein-coupled receptor. Optimization of fragments exploring two binding site subpockets was probed by calculating relative binding affinities for 23 adenine derivatives, resulting in strong agreement with experimental data (R2 = 0.78). The predictive power of MD/FEP was significantly better than that of an empirical scoring function. We also demonstrated the potential of the MD/FEP to assess multiple binding modes and to tailor the thermodynamic profile of ligands during optimization. Finally, MD/FEP was applied prospectively to optimize three nonpurine fragments, and predictions for 12 compounds were evaluated experimentally. The direction of the change in binding affinity was correctly predicted in a majority of the cases, and agreement with experiment could be improved with rigorous parameter derivation. The results suggest that MD/FEP will become a powerful tool in structure-driven optimization of fragments to lead candidates.

Adenosine derivatives developed to activate adenosine receptors (ARs) revealed µM activity at serotonin 5HT2B and 5HT2C receptors (5HTRs). We explored the SAR at 5HT2Rs and modeled receptor interactions in order to optimize affinity and simultaneously reduce AR affinity. Depending on N6 substitution, small 5′-alkylamide modification maintained 5HT2BR affinity, which was enhanced upon ribose substitution with rigid bicyclo[3.1.0]hexane (North (N)-methanocarba), e.g. N6-dicyclopropylmethyl 4′-CH2OH derivative 14 (Ki 11 nM). 5′-Methylamide 23 was 170-fold selective as antagonist for 5HT2BR vs. 5HT2CR. 5′-Methyl 25 and ethyl 26 esters potently antagonized 5HT2Rs with moderate selectivity in comparison to ARs; related 6-N,N-dimethylamino analogue 30 was 5HT2R-selective. 5′ position flexibility of substitution was indicated in 5HT2BR docking. Both 5′-ester and 5′-amide derivatives displayed in vivo t1/2 of 3–4 h. Thus, we used GPCR modeling to repurpose nucleoside scaffolds in favor of binding at nonpurine receptors, as novel 5HT2R antagonists, with potential for cardioprotection, liver protection or CNS activity.

We have repurposed (N)-methanocarba adenosine derivatives (A3 adenosine receptor (AR) agonists) to enhance radioligand binding allosterically at the human dopamine (DA) transporter (DAT) and inhibit DA uptake. We extended the structure-activity relationship of this series with small N6-alkyl substitution, 5′-esters, deaza modifications of adenine, and ribose restored in place of methanocarba. C2-(5-halothien-2-yl)-ethynyl 5′-methyl 9 (MRS7292) and 5′-ethyl 10 (MRS7232) esters enhanced binding at DAT (EC50 ∼35 nM) and at norepinephrine transporter (NET). 9 and 10 were selective for DAT compared to A3AR in the mouse, but not human. At DAT, binding of two structurally dissimilar radioligands was enhanced; NET binding of only one radioligand was enhanced; SERT radioligand binding was minimally affected. 10 was more potent than cocaine at inhibiting DA uptake (IC50 = 107 nM). Ribose analogues were weaker in DAT interaction than corresponding bicyclics. Thus, we enhanced the neurotransmitter transporters activity of rigid nucleosides while reducing A3AR affinity.

Small molecule screening libraries cover only a small fraction of the astronomical number of possible drug-like compounds, limiting the success of ligand discovery efforts. Computational screening of virtual libraries representing unexplored chemical space could potentially bridge this gap. Drug development for adenosine receptors (ARs) as targets for inflammation and cardiovascular diseases has been hampered by the paucity of agonist scaffolds. To identify novel AR agonists, a virtual library of synthetically tractable nucleosides with alternative bases was generated and structure-based virtual screening guided selection of compounds for synthesis. Pharmacological assays were carried out at three AR subtypes for 13 ribosides. Nine compounds displayed significant activity at the ARs, and several of these represented atypical agonist scaffolds. The discovered ligands also provided insights into receptor activation and revealed unknown interactions of endogenous and clinical compounds with the ARs. The results demonstrate that virtual compound databases provide access to bioactive matter from regions of chemical space that are sparsely populated in commercial libraries, an approach transferrable to numerous drug targets.

While screening off-target effects of rigid (N)-methanocarba-adenosine 5′-methylamides as A3 adenosine receptor (AR) agonists, we discovered μM binding hits at the δ-opioid receptor (DOR) and translocator protein (TSPO). In an effort to increase OR and decrease AR affinity by structure activity analysis of this series, antagonist activity at κ-(K)OR appeared in 5′-esters (ethyl 24 and propyl 30), which retained TSPO interaction (μM). 7-Deaza modification of C2-(arylethynyl)-5′-esters but not 4′-truncation enhanced KOR affinity (MRS7299 28 and 29, Ki ≈ 40 nM), revealed μ-OR and DOR binding, and reduced AR affinity. Molecular docking and dynamics simulations located a putative KOR binding mode consistent with the observed affinities, placing C7 in a hydrophobic region. 3-Deaza modification permitted TSPO but not OR binding, and 1-deaza was permissive to both; ribose-restored analogues were inactive at both. Thus, we have repurposed a known AR nucleoside scaffold for OR antagonism, with a detailed hypothesis for KOR recognition.

Purine (N)-methanocarba-5′-N-alkyluronamidoriboside A3 adenosine receptor (A3AR) agonists lacking an exocyclic amine resulted from an unexpected reaction during a Sonogashira coupling and subsequent aminolysis. Because the initial C6-Me and C6-styryl derivatives had unexpectedly high A3AR affinity, other rigid nucleoside analogues lacking an exocyclic amine were prepared. Of these, the C6-Me-(2-phenylethynyl) and C2-(5-chlorothienylethynyl) analogues were particularly potent, with human A3AR Ki values of 6 and 42 nM, respectively. Additionally, the C2-(5-chlorothienyl)-6-H analogue was potent and selective at A3AR (MRS7220, Ki 60 nM) and also completely reversed mouse sciatic nerve mechanoallodynia (in vivo, 3 μmol/kg, po). The lack of a C6 H-bond donor while maintaining A3AR affinity and efficacy could be rationalized by homology modeling and docking of these hypermodified nucleosides. The modeling suggests that a suitable combination of stabilizing features can partially compensate for the lack of an exocyclic amine, an otherwise important contributor to recognition in the A3AR binding site.

Background: To determine the prevalence of prosthetic joint infections (PJIs) after elective clean hand surgery in order to determine whether prophylactic antibiotics are warranted in patients who have previously undergone total joint arthroplasty (TJA). Methods: All patients undergoing elective clean hand surgery between 2012 and 2018 were retrospectively cross-referenced with patients who had previously undergone a TJA at the same urban academic medical center. Inclusion criteria were any patients who underwent clean hand surgery during the study period who were an adult between the ages of 30 and 90, had a previous TJA, and did not have a previous history of a PJI. All charts were reviewed to collect data on patient demographics, co-morbidities, the type of TJA and hand surgery performed, whether prophylactic antibiotics were used prior to the hand surgery, and whether a PJI occurred within 3 months of the hand surgery. Results: Total of 331 patients (181 females and 150 males) were identified over the 6-year period that met inclusion criteria. In total, 13% of the patients received prophylactic antibiotics prior to their hand surgery and 87% had not. Only 1 case of a PJI occurred within 3 months of a hand surgery. No relationship was identified between the PJI and the hand surgery, nor the need for preoperative antibiotic prophylaxis. Conclusions: Incidence of PJI after clean hand surgery is very low. We do not recommend the routine use of antibiotic prophylaxis in patients undergoing clean elective hand surgery with a history of prior TJA in order to prophylax against a PJI.

Health care increasingly collects patient-reported outcomes (PROs) via web-based platforms. The purpose of this study was to evaluate how patient age influences portal engagement. Patients undergoing elective surgery at a single multispecialty orthopedic practice from September 2014 to February 2017 had access to an online portal to complete PROs, message the clinic, and view physical therapy instructions. A mobile app was optionally available. Age, sex, log-in frequency, PRO completion rates, and number of messages sent were reviewed retrospectively. Message frequency, log-in rates, and PRO compliance were highest for patients aged 41 to 50, 51 to 60, and 61 to 70, respectively. Mobile app use decreased with age ( P = .002); yet, at all ages, the mobile app group was more engaged. In particular, for patients aged 18 to 30 years, log-in frequency increased 2.5-fold and PRO compliance improved 44% ( P < .001) in the mobile app group. This study demonstrates that portal interaction varies by age and that data capture is highest in patients who choose the mobile app.