Schematic model of the agonist-induced μOR conformational change into an active-like state.

<p>Schematic model of the agonist-induced μOR conformational change into an active-like state.</p

Molecular structures of morphine and hydromorphone.

<p>Molecular structures of morphine and hydromorphone.</p

Free energy differences (in kcal/mol) for the described transformations.

<p>Error estimates are included.</p><p>^a Calculated as </p><p></p><p></p><p><mi>Δ</mi><mi>Δ</mi></p><p><mi>G</mi></p><p>MOP<mo>→</mo>HMP</p><p>exp<mo>.</mo></p><p></p><mo>=</mo><mi>Δ</mi><p><mi>G</mi></p><p>bind</p><p>HMP<mo stretchy="false">(</mo>exp<mo>.</mo><mo stretchy="false">)</mo></p><p></p><mo>−</mo><mi>Δ</mi><p><mi>G</mi></p><p>bind</p><p>MOP<mo stretchy="false">(</mo>exp<mo>.</mo><mo stretchy="false">)</mo></p><p></p><mo>=</mo><mi>R</mi><mi>T</mi>ln<p><mo>[</mo></p><p></p><p></p><p></p><p><mi>K</mi><mi>i</mi></p><p>HMP<mo stretchy="false">(</mo>exp<mo>.</mo><mo stretchy="false">)</mo></p><p></p><p></p><mo>/</mo><p></p><p><mi>K</mi><mi>i</mi></p><p>MOP<mo stretchy="false">(</mo>exp<mo>.</mo><mo stretchy="false">)</mo></p><p></p><p></p><p></p><p></p><mo>]</mo><p></p><mo>.</mo><p></p><p></p><p></p><p></p><p>Free energy differences (in kcal/mol) for the described transformations.</p

Representative structure of the MD simulations for (A) the MOP-μOR and (B) the HMP-μOR complexes obtained from clustering analysis.

<p>The ligand carbon atoms are in orange. H-bonds and salt-bridges are shown in green and magenta dashed lines, respectively. For clarity hydrogen atoms of the ligands and the μOR residues are not shown. H297 is monoprotonated at the Nε atom.</p

Conformational change of μOR EL3 observed in the case of MOP binding.

<p>E310 in EL3 forms a salt-bridge with K233 (magenta dashed lines), which remains until the end of the simulation.</p

Arrangements of aromatic residues at the μOR orthosteric binding site upon binding with (A) MOP and with (B) HMP.

<p>Arrangements of aromatic residues at the μOR orthosteric binding site upon binding with (A) MOP and with (B) HMP.</p

Minimum distances between both morphinan drugs (MOP and HMP) and selected protein residues.

<p>Distances are given in Å and averaged over the finite temperature MD trajectories.</p><p>Minimum distances between both morphinan drugs (MOP and HMP) and selected protein residues.</p

The thermodynamic cycle for computing the free energy difference between MOP and HMP upon binding to μOR: ΔΔGbind=ΔGbindMOP−ΔGbindHMP=ΔGMOP→HMPbound−ΔGMOP→HMPunbound.

<p>The unbound state requires transformation of the ligands alone in solution, since the receptor is the same in both cases.</p

Quantitative Assessment of Drug Delivery to Tissues and Association with Phospholipidosis: A Case Study with Two Structurally Related Diamines in Development

Drug induced phospholipidosis (PLD) may be observed in the preclinical phase of drug development and pose strategic questions. As lysosomes have a central role in pathogenesis of PLD, assessment of lysosomal concentrations is important for understanding the pharmacokinetic basis of PLD manifestation and forecast of potential clinical appearance. Herein we present a systematic approach to provide insight into tissue-specific PLD by evaluation of unbound intracellular and lysosomal (reflecting acidic organelles) concentrations of two structurally related diprotic amines, GRT1 and GRT2. Their intratissue distribution was assessed using brain and lung slice assays. GRT1 induced PLD both <i>in vitro</i> and <i>in vivo</i>. GRT1 showed a high intracellular accumulation that was more pronounced in the lung, but did not cause cerebral PLD due to its effective efflux at the blood–brain barrier. Compared to GRT1, GRT2 revealed higher interstitial fluid concentrations in lung and brain, but more than 30-fold lower lysosomal trapping capacity. No signs of PLD were seen with GRT2. The different profile of GRT2 relative to GRT1 is due to a structural change resulting in a reduced basicity of one amino group. Hence, by distinct chemical modifications, undesired lysosomal trapping can be separated from desired drug delivery into different organs. In summary, assessment of intracellular unbound concentrations was instrumental in delineating the intercompound and intertissue differences in PLD induction <i>in vivo</i> and could be applied for identification of potential lysosomotropic compounds in drug development

Discovery of a Potent Analgesic NOP and Opioid Receptor Agonist: Cebranopadol

In a previous communication, our efforts leading from <b>1</b> to the identification of spiro­[cyclohexane-dihydropyrano­[3,4-<i>b</i>]­indole]-amine <b>2a</b> as analgesic NOP and opioid receptor agonist were disclosed and their favorable in vitro and in vivo pharmacological properties revealed. We herein report our efforts to further optimize lead <b>2a</b>, toward <i>trans</i>-6′-fluoro-4′,9′-dihydro-<i>N</i>,<i>N</i>-dimethyl-4-phenyl-spiro­[cyclohexane-1,1′(3′<i>H</i>)-pyrano­[3,4-<i>b</i>]­indol]-4-amine (cebranopadol, <b>3a</b>), which is currently in clinical development for the treatment of severe chronic nociceptive and neuropathic pain