Injectable Systems for Long-Lasting Insulin Therapy

Diabetes mellitus is one of the major global health problems and the prevalence rate is ever increasing reaching to 48% increase by the year of 2040 causing significant economic burdens. Insulin therapy has been the mainstay of diabetes treatment since its discovery in 1922. However, insulin is an unstable peptide with a half-life of only 4-6 min which poses significant challenge in prolonging duration of action of insulin. Nevertheless, the advances in recombinant DNA technology and protein engineering have enabled the development of several long-acting insulin analogue products which show duration of action up to 42 h. However, these insulin analogues still require once- or twice-daily injections for optimal glycemic control resulting in poor compliance and adherence issues among patients. To achieve insulin release for more than one day, different injectable delivery systems including microspheres, in situ forming depots, nanoparticles and composite systems have been developed for sustained release of insulin for days to weeks in in vitro and preclinical studies. Several of these delivery systems have further advanced to clinical trials for once-weekly insulin injection to treat diabetes. Although a number of review articles have appeared in the literature to discuss the developments of long-acting insulin analogues and sustained release insulin delivery systems, none of them comprehensively cover the whole area starting all the way from prototype design and preclinical studies to clinical trials and marketed products. The scope of this review is to fill in the gap and comprehensively summarize the developments of injectable insulin analogues and delivery systems for long-term glycemic control and improved patient compliance

Design, Synthesis, and Preliminary Evaluation of a Potential Synthetic Opioid Rescue Agent

BACKGROUND: One of the most prominent opioid analgesics in the United States is the high potency agonist fentanyl. It is used in the treatment of acute and chronic pain and as an anesthetic adjuvant. When used inappropriately, however, ingestion of just a few milligrams of fentanyl or other synthetic opioid can cause opioid-induced respiratory depression (OIRD), often leading to death. Currently, the treatment of choice for OIRD is the opioid receptor antagonist naloxone. Recent reports, however, suggest that higher doses or repeated dosing of naloxone (due to recurrence of respiratory depression) may be required to reverse fully fentanyl-induced respiratory depression, rendering this treatment inadequate. To combat this synthetic opioid overdose crisis, this research aims at identifying a novel opioid reversal agent with enhanced efficacy towards fentanyl and other synthetic opioids. METHODS: A series of naltrexone analogues were characterized for their ability to antagonize the effects of fentanyl in vitro utilizing a modified forskolin-induced cAMP accumulation assay. Lead analogue 29 was chosen to undergo further PK studies, followed by in vivo pharmacological analysis to determine its ability to antagonize opioid-induced antinociception in the hot plate assay. RESULTS: A series of potent MOR antagonists were identified, including the highly potent analogue 29 (IC50 = 2.06 nM). Follow-up PK studies revealed 29 to possess near 100% bioavailability following IP administration. Brain concentrations of 29 surpassed plasma concentrations, with an apparent terminal half-life of ~ 80 min in mice. In the hot plate assay, 29 dose-dependently (0.01–0.1 mg/kg; IP) and fully antagonized the antinociception induced by oxycodone (5.6 mg/kg; IP). Furthermore, the dose of 29 that is fully effective in preventing oxycodone-induced antinociception (0.1 mg/kg) was ineffective against locomotor deficits caused by the KOR agonist U50,488. CONCLUSIONS: Methods have been developed that have utility to identify enhanced rescue agents for the treatment of OIRD. Analogue 29, possessing potent MOR antagonist activity in vitro and in vivo, provides a promising lead in our search for an enhanced synthetic opioid rescue agent