Synthesis and Evaluation of in Vivo Anti-hypothermic Effect of the N- and C-Terminus Modified Thyrotropin-Releasing Hormone Mimetic: [(4S,5S)-(5-Methyl-2-oxooxazolidine-4-yl)carbonyl]-[3-(thiazol-4-yl)-L-alanyl]-L-prolinamide.

We explored orally effective thyrotropin-releasing hormone (TRH) mimetics, which show high central nervous system effects in structure-activity relationship studies based on in vivo antagonistic activity on reserpine-induced hypothermia (anti-hypothermic effect) in mice starting from TRH. This led us to the TRH mimetic: [(4S,5S)-(5-methyl-2-oxooxazolidine-4-yl)carbonyl]-[3-(thiazol-4-yl)-L-alanyl]-L-prolinamide 1, which shows a higher anti-hypothermic effect compared with that of TRH after oral administration. We next attempted further chemical modification of the N- and C-terminus of 1 to find more orally effective TRH mimetics. As a result, we obtained several N- and C-terminus modified TRH mimetics which showed high anti-hypothermic effects.

Correction to Discovery of the Orally Effective Thyrotropin-Releasing Hormone Mimetic: 1-{N-[(4S,5S)-(5-Methyl-2-oxooxazolidine-4-yl)carbonyl]-3-(thiazol-4-yl)-l-alanyl}-(2R)-2-methylpyrrolidine Trihydrate (Rovatirelin Hydrate).

[This corrects the article DOI: 10.1021/acsomega.8b01481.].

Pharmacologic effects of naldemedine, a peripherally acting µ-opioid receptor antagonist, in in vitro and in vivo models of opioid-induced constipation.

BACKGROUND: Naldemedine (S-297995) is a peripherally acting µ-opioid receptor antagonist developed as a once-daily oral drug for opioid-induced constipation (OIC) in adults with chronic noncancer or cancer pain. This study characterized the pharmacological effects of naldemedine in vitro and in vivo. METHODS: The binding affinity and antagonist activity of naldemedine against recombinant human µ-, δ-, and κ-opioid receptors were assayed in vitro. Pharmacologic effects of naldemedine were investigated using animal models of morphine-induced inhibition of small and large intestinal transit, castor oil-induced diarrhea, antinociception, and morphine withdrawal. KEY RESULTS: Naldemedine showed potent binding affinity and antagonist activities for recombinant human µ-, δ-, and κ-opioid receptors. Naldemedine significantly reduced opioid-induced inhibition of small intestinal transit (0.03-10 mg kg-1 ; P < 0.05) and large intestinal transit (0.3-1 µmol L-1 ; P < 0.05). Naldemedine (0.03-1 mg kg-1 ) pretreatment significantly reversed the inhibition of castor oil-induced diarrhea by subcutaneous morphine (P < 0.01). Naldemedine (1-30 mg kg-1 ) pretreatment (1 or 2 hours) did not alter the analgesic effects of morphine in a model measuring the latency of a rat to flick its tail following thermal stimulation. However, a significant delayed reduction of the analgesic effect of morphine was seen with higher doses of naldemedine (10-30 mg kg-1 ). Some centrally mediated and peripherally mediated withdrawal signs in morphine-dependent rats were seen with naldemedine doses ≥3 and ≥0.3 mg kg-1 , respectively. CONCLUSIONS & INFERENCES: Naldemedine displayed potent binding affinity to, and antagonistic activity against, µ-, δ-, and κ-opioid receptors. Naldemedine tempered OIC in vivo without compromising opioid analgesia.

Discovery of the Orally Effective Thyrotropin-Releasing Hormone Mimetic: 1-{N-[(4S,5S)-(5-Methyl-2-oxooxazolidine-4-yl)carbonyl]-3-(thiazol-4-yl)-l-alanyl}-(2R)-2-methylpyrrolidine Trihydrate (Rovatirelin Hydrate).

We have explored orally effective thyrotropin-releasing hormone (TRH) mimetics, showing oral bioavailability and brain penetration by structure-activity relationship (SAR) study on the basis of in vivo antagonistic activity on reserpine-induced hypothermia in mice. By primary screening of the synthesized TRH mimetics, we found a novel TRH mimetic: l-pyroglutamyl-[3-(thiazol-4-yl)-l-alanyl]-l-prolinamide with a high central nervous system effect compared with TRH as a lead compound. Further SAR optimization studies of this lead compound led to discovery of a novel orally effective TRH mimetic: 1-{N-[(4S,5S)-(5-methyl-2-oxooxazolidine-4-yl)carbonyl]-3-(thiazol-4-yl)-l-alanyl}-(2R)-2-methylpyrrolidine trihydrate (rovatirelin hydrate), which was selected as a candidate for clinical trials.

Distinct relations among plasma concentrations required for different pharmacological effects in oxycodone, morphine, and fentanyl.

Several clinical reports showed that adverse effect profiles are not the same in morphine, oxycodone, and fentanyl. The authors investigated whether the relationship between plasma concentrations for antinociceptive effect and for various pharmacological effects differed among oxycodone, morphine, and fentanyl under controlled experimental setting using animal models. Oxycodone induced constipation and an antinociceptive effect in a similar concentration-dependent manner, whereas morphine required approximately 9-fold higher plasma concentration for antinociceptive effect compared with that for constipation when 50% effective plasma concentration (EC(50)) levels were compared. The EC(50) values for inhibition of behavioral activity were 2.1-, 2.7-, and 1.3-fold higher than those for antinociceptive effect in oxycodone, morphine, and fentanyl, respectively. Respiratory inhibition was observed even at higher plasma concentrations in all three opioids, and the differences in the EC(50) values compared with those for antinociceptive effects were 234.5-fold (oxycodone), 233.1-fold (morphine), or 104.2-fold (fentanyl). These results showed that oxycodone, morphine, and fentanyl exhibited unique patterns of plasma concentrations required for different pharmacological effects. The different adverse effect profiles observed in a clinical setting appear to be resulted from, at least in part, distinct intrinsic pharmacological profiles among these µ-opioid receptor agonists.

Morphine, oxycodone, and fentanyl exhibit different analgesic profiles in mouse pain models.

Morphine, oxycodone, and fentanyl are clinically prescribed drugs for the management of severe pain. We investigated whether these opioids possess different efficacy profiles on several types of pain in mouse pain models. When the three opioids were tested in the femur bone cancer model, all of them significantly reversed guarding behavior, whereas the effects on limb-use abnormality and allodynia-like behavior differed among the opioids. Particularly, although oxycodone (5 - 20 mg/kg) and fentanyl (0.2 mg/kg) significantly reversed limb-use abnormality, not even a high dose of morphine (50 mg/kg) could reverse it. When the effects of these opioids were examined in a sciatic nerve ligation (SNL) model of neuropathic pain, oxycodone was the most effective, producing an antinociceptive effect without affecting the withdrawal threshold of sham-treated animals. When the effects of these opioids were examined with the tail-flick test using naive animals, oxycodone, morphine, and fentanyl exhibited antinociceptive effects on thermal nociception. These results show that the three opioids exhibit different efficacy outcomes in multiple pain models and that the efficacy profile of oxycodone does not overlap those of morphine and fentanyl.

Oxycodone-induced analgesic effects in a bone cancer pain model in mice.

The femur bone cancer pain model was developed by implanting mouse osteolytic tumor cells (NCTC 2472) into the intramedulla of the femur in C3H/HeN mice. In vivo imaging analysis revealed that the implanted tumor cells grew progressively over 14 days. Associated with the tumor growth, guarding behavior, which was an indication of ongoing pain, time-dependently increased. Limb use abnormality and allodynia, which were indications of ambulatory and neuropathic pain, respectively, also appeared. The analgesic effects of oxycodone and other opioids, such as morphine and fentanyl, were evaluated at 14 days when all pain-related behaviors clearly appeared. Oxycodone (2-20 mg/kg, s.c.), morphine (10-50 mg/kg, s.c.) and fentanyl (0.05-0.2 mg/kg, s.c.) significantly reduced guarding behavior. Oxycodone (5-20 mg/kg, s.c.) and fentanyl (0.1 and 0.2 mg/kg, s.c.) significantly reversed limb use abnormality, but morphine (5-50 mg/kg, s.c.) did not. Moreover, oxycodone (5-20 mg/kg, s.c.) dose-dependently reversed allodynia without affecting the sham-treated mice. Morphine (50 mg/kg, s.c.) and fentanyl (0.075-0.2 mg/kg, s.c.) also reversed allodynia, but morphine (50 mg/kg, s.c.) tended to affect and fentanyl (0.1 and 0.2 mg/kg, s.c.) affected the withdrawal threshold in sham-treated mice. These results suggested that oxycodone relieved not only ongoing pain, but also ambulatory and neuropathic pain, and that the analgesic profile of oxycodone could be different from that of either morphine or fentanyl.

BACE1 inhibition reduces endogenous Abeta and alters APP processing in wild-type mice.

Accumulation of amyloid beta peptide (Abeta) in brain is a hallmark of Alzheimer's disease (AD). Inhibition of beta-site amyloid precursor protein (APP)-cleaving enzyme-1 (BACE1), the enzyme that initiates Abeta production, and other Abeta-lowering strategies are commonly tested in transgenic mice overexpressing mutant APP. However, sporadic AD cases, which represent the majority of AD patients, are free from the mutation and do not necessarily have overproduction of APP. In addition, the commonly used Swedish mutant APP alters APP cleavage. Therefore, testing Abeta-lowering strategies in transgenic mice may not be optimal. In this study, we investigated the impact of BACE1 inhibition in non-transgenic mice with physiologically relevant APP expression. Existing Abeta ELISAs are either relatively insensitive to mouse Abeta or not specific to full-length Abeta. A newly developed ELISA detected a significant reduction of full-length soluble Abeta 1-40 in mice with the BACE1 homozygous gene deletion or BACE1 inhibitor treatment, while the level of x-40 Abeta was moderately reduced due to detection of non-full-length Abeta and compensatory activation of alpha-secretase. These results confirmed the feasibility of Abeta reduction through BACE1 inhibition under physiological conditions. Studies using our new ELISA in non-transgenic mice provide more accurate evaluation of Abeta-reducing strategies than was previously feasible.