Long-term Safety and Tolerability of NKTR-181 in Patients with Moderate to Severe Chronic Low Back Pain or Chronic Noncancer Pain: A Phase 3 Multicenter, Open-Label, 52-Week Study (SUMMIT-08 LTS)

All-Hydrocarbon Stapled Peptide Multifunctional Agonists at Opioid and Neuropeptide FF Receptors: Highly Potent, Long-Lasting Brain Permeant Analgesics with Diminished Side Effects

Our previous study reported the multifunctional agonist for opioid and neuropeptide FF receptors DN-9, along with its cyclic peptide analogues c[D-Cys2, Cys5]-DN-9 and c[D-Lys2, Asp5]-DN-9. These analogues demonstrated potent antinociceptive effects with reduced opioid-related side effects. To develop more stable and effective analgesics, we designed, synthesized, and evaluated seven hydrocarbon-stapled cyclic peptides based on DN-9. In vitro calcium mobilization assays revealed that most of the stapled peptides, except 3, displayed multifunctional agonistic activities at opioid and neuropeptide FF receptors. Subcutaneous administration of all stapled peptides resulted in effective and long-lasting antinociceptive activities lasting up to 360 min. Among these stapled peptides, 1a and 1b emerged as the optimized compounds, producing potent central antinociception following subcutaneous, intracerebroventricular, and oral administrations. Additionally, subcutaneous administration of 1a and 1b caused nontolerance antinociception, with limited occurrence of constipation and addiction. Furthermore, 1a was selected as the final optimized compound due to its wider safety window compared to 1b.

Estimating the population health burden of musculoskeletal conditions using primary care electronic health records

OBJECTIVES

Better indicators from affordable, sustainable data sources are needed to monitor population burden of musculoskeletal conditions. We propose five indicators of musculoskeletal health and assessed if routinely available primary care electronic health records (EHR) can estimate population levels in musculoskeletal consulters.

METHODS

We collected validated patient-reported measures of pain experience, function and health status through a local survey of adults (≥35 years) presenting to English general practices over 12 months for low back pain, shoulder pain, osteoarthritis and other regional musculoskeletal disorders. Using EHR data we derived and validated models for estimating population levels of five self-reported indicators: prevalence of high impact chronic pain, overall musculoskeletal health (based on Musculoskeletal Health Questionnaire), quality of life (based on EuroQoL health utility measure), and prevalence of moderate-to-severe low back pain and moderate-to-severe shoulder pain. We applied models to a national EHR database (Clinical Practice Research Datalink) to obtain national estimates of each indicator for three successive years.

RESULTS

The optimal models included recorded demographics, deprivation, consultation frequency, analgesic and antidepressant prescriptions, and multimorbidity. Applying models to national EHR, we estimated that 31.9% of adults (≥35 years) presenting with non-inflammatory musculoskeletal disorders in England in 2016/17 experienced high impact chronic pain. Estimated population health levels were worse in women, older aged and those in the most deprived neighbourhoods, and changed little over 3 years.

CONCLUSION

National and subnational estimates for a range of subjective indicators of non-inflammatory musculoskeletal health conditions can be obtained using information from routine electronic health records.

Preclinical Assessment of the Analgesic Pharmacology of NKTR-181 in Rodents

OBJECTIVE

Pharmacological evaluation of the mu-opioid receptor (MOR) agonist properties of NKTR-181 in rodent models.

METHODS

Graded noxious stimulus intensities were used in rats to establish the antinociceptive potency and efficacy of NKTR-181 relative to morphine, fentanyl, and oxycodone. Characteristics of MOR agonist actions, as measured by antinociceptive tolerance and cross-tolerance, as well as opioid-induced hyperalgesia (OIH) and naloxone-precipitated withdrawal in NKTR-181- and morphine-dependent in mice, were compared.

RESULTS

NKTR-181 showed dose- and time-related antinociception with similar maximal effects to morphine in the rat and mouse hot-water tail-flick test. No sex or species differences were observed in NKTR-181 or morphine antinociception. Rats treated with NKTR-181 and morphine exhibited decreases in both potency and maximal efficacy as nociceptive stimulus intensity was increased from a water temperature of 50 °C to 54 °C. Evaluation of antinociception at a high stimulus intensity revealed that oxycodone and fentanyl exhibited greater efficacy than either NKTR-181 or morphine. The relative potency difference between NKTR-181 and morphine across all tail-flick studies was determined to be 7.6-fold (90% confidence interval, 2.6, 21.5). The peak antinociceptive effect of NKTR-181 was delayed compared to that of the other opioids and cumulative drug effects were not observed. Repeated treatment with escalating, approximately equi-analgesic doses of NKTR-181 or morphine, produced antinociceptive tolerance and cross-tolerance. Under these pharmacological conditions, OIH and naloxone-precipitated physical dependence were similar for NKTR-181 and morphine.

CONCLUSIONS

NKTR-181 had a slower onset, but similar efficacy, to morphine in the models studied supporting reduced abuse potential while maintaining analgesic effect in comparison with current opioids.

Anesthetic and Analgesic Drug Products Advisory Committee Activity and Decisions in the Opioid-crisis Era

The United States Food and Drug Administration is tasked with ensuring the efficacy and safety of medications marketed in the United States. One of their primary responsibilities is to approve the entry of new drugs into the marketplace, based on the drug’s perceived benefit–risk relationship. The Anesthetic and Analgesic Drug Product Advisory Committee is composed of experts in anesthesiology, pain management, and biostatistics, as well as consumer and industry representatives, who meet several times annually to review new anesthetic-related drugs, those seeking new indications, and nearly every opioid-related application for approval. The following report describes noteworthy activities of this committee since 2017, as it has grappled, along with the Food and Drug Administration, to balance the benefit–risk relationships for individual patients along with the overarching public health implications of bringing additional opioids to market. All anesthesia advisory committee meetings since 2017 will be described, and six will be highlighted, each with representative considerations for potential new opioid formulations or local anesthetics.

Measuring Opioid Withdrawal in a Phase 3 Study of a New Analgesic, NKTR-181 (Oxycodegol), in Patients with Moderate to Severe Chronic Low Back Pain

OBJECTIVE

To evaluate the SUMMIT-07 trial opioid withdrawal results of NKTR-181 (oxycodegol), a new molecular entity mu-opioid receptor agonist.

DESIGN

Phase 3, enriched-enrollment, double-blind, randomized-withdrawal study in patients with chronic low back pain (CLBP).

SETTING

Conducted in the United States at multiple sites.

METHODS

SUMMIT-07 was comprised of five periods: screening; NKTR-181 open-label titration (100 to 400 mg twice daily); 12-week randomized, double-blind study drug (NKTR-181 or placebo); one-week study drug taper; and two-week safety follow-up. Permitted rescue medication included hydrocodone 5 mg/acetaminophen 300 mg (two tablets daily) for two weeks after randomization, then acetaminophen 1.0 gm daily for the remainder of the trial. Signs and symptoms of drug withdrawal were evaluated using the Clinical Opiate Withdrawal Scale (COWS); Subjective Opiate Withdrawal Scale (SOWS); Misuse, Abuse, and Diversion Drug Event Reporting System (MADDERS); and withdrawal-related adverse events.

RESULTS

Of 1,190 patients entering titration, one patient had moderate withdrawal (COWS score 13/48 maximum) three days after discontinuing NKTR-181. Of 610 patients randomized (N = 309, NKTR-181; N = 301, placebo), no COWS scores indicating withdrawal at a moderate level or greater (i.e., score ≥13) were observed at any time point. At day 8 after randomization, week 12, and the end of tapering, COWS scores indicating mild withdrawal (<13) were observed in seven (2.4%), one (0.4%), and one (0.5%) placebo patients, respectively, and three (1.0%), one (0.4%), and five (2.3%) NKTR-181 patients, respectively. Mean SOWS scores in both arms were ≤2.8 of 64 possible points at all time points. During the randomized period, of 35 events identified by MADDERS, adjudicators identified 20 possible "withdrawal" events (9 [2.9%] NKTR-181 and 11 [3.7%] placebo).

CONCLUSIONS

NKTR-181 exhibited a low rate and severity of opioid withdrawal in SUMMIT-07 patients with CLBP.

Are Opioids Needed to Treat Chronic Low Back Pain? A Review of Treatment Options and Analgesics in Development

The continued prevalence of chronic low back pain (CLBP) is a testament to our lack of understanding of the potential causes, leading to significant treatment challenges. CLBP is the leading cause of years lived with disability and the fifth leading cause of disability-adjusted life-years. No single non-pharmacologic, pharmacologic, or interventional therapy has proven effective as treatment for the majority of patients with CLBP. Although non-pharmacologic therapies are generally helpful, they are often ineffective as monotherapy and many patients lack adequate access to these treatments. Noninvasive treatment measures supported by evidence include physical and chiropractic therapy, yoga, acupuncture, and non-opioid and opioid pharmacologic therapy; data suggest a moderate benefit, at most, for any of these therapies. Until our understanding of the pathophysiology and treatment of CLBP advances, clinicians must continue to utilize rational multimodal treatment protocols. Recent Centers for Disease Control and Prevention guidelines for opioid prescribing recommend that opioids not be utilized as first-line therapy and to limit the doses when possible for fear of bothersome or dangerous adverse effects. In combination with the current opioid crisis, this has caused providers to minimize or eliminate opioid therapy when treating patients with chronic pain, leaving many patients suffering despite optimal nonopioid therapies. Therefore, there remains an unmet need for effective and tolerable opioid receptor agonists for the treatment of CLBP with improved safety properties over legacy opioids. There are several such agents in development, including opioids and other agents with novel mechanisms of action. This review critiques non-pharmacologic and pharmacologic treatment modalities for CLBP and examines the potential of novel opioids and other analgesics that may be a useful addition to the treatment options for patients with chronic pain.

Human Abuse Potential of Oral NKTR-181 in Recreational Opioid Users: A Randomized, Double-Blind, Crossover Study

OBJECTIVE

To evaluate the human abuse potential, pharmacokinetics, pharmacodynamics, and safety of oral NKTR-181 (oxycodegol), a novel full mu-opioid receptor agonist, relative to oral oxycodone.

DESIGN

This double-blind, randomized, single-dose, crossover human abuse potential study was conducted in healthy, adult, non-physically dependent recreational opioid users.

SETTING

Inpatient clinical research site.

SUBJECTS

Seventy-one subjects randomized (95.7% male, 65.2% African American, mean age = 31.7 years).

METHODS

The primary objective was to compare two therapeutic doses of NKTR-181 (400 and 600 mg) with 40 and 60 mg of oxycodone and a supratherapeutic dose (1200 mg) of NKTR-181 with 60 mg of oxycodone using visual analog scale (VAS) ratings for Drug Liking "at this moment" (Drug Liking). Secondary objectives included VAS ratings for other subjective measures, and central nervous system (CNS) mu-opioid effects were assessed using pupillometry. Each subject received single oral doses of five treatments and matching placebo.

RESULTS

Compared with 40 and 60 mg of oxycodone, the maximum mean Drug Liking score at 400 and 600 mg NKTR-181 was significantly lower, and the rate of onset and extent of Drug Liking for all NKTR-181 doses in the first two hours postdose were also significantly lower. Delayed attenuated Drug Liking and pupillary miosis response following administration of NKTR-181 vs oxycodone were consistent with slower NKTR-181 CNS entry kinetics and mu-opioid receptor binding. No adverse events were rated as severe, and somnolence and dizziness occurred more frequently when subjects received oxycodone.

CONCLUSIONS

NKTR-181 at oral doses of 400 and 600 mg showed significantly fewer and less severe subjective effects accepted as representative of opioid abuse potential, such as lower peak Drug Liking in recreational opioid users, than 40 and 60 mg of oxycodone.