PAINWeek National Conference
PAINWeek National Conference
September 15, 2017
2 min read

Two studies show promising results for NKTR-181

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Steve Doberstein
Steve Doberstein

Patients receiving the opioid analgesic NKTR-181 had reduced back pain and exhibited low rates of opioid withdrawal, compared their counterparts who took a placebo, according to two separate posters presented at PAINWeek.

“As the first oral, full µ-opioid agonist molecule to be developed in nearly 100 years, NKTR-181's unique inherent properties could not only help stem the rate of new addiction with conventional opioids, but also reduce diversion of prescription medicines for abuse,” Steve Doberstein, PhD, senior vice president and chief scientific officer, Nektar Therapeutics, told Healio Family Medicine. “NKTR-181 could provide an alternative that both patients and physicians will feel better about using.”

Both posters contained results from the randomized, doubleblind SUMMIT-07 study comparing NKTR-181 with placebo in 610 opioid-nave adult patients. Patients had moderate to severe chronic, non-neuropathic, low-back pain for at least 6 months, and had been treated inadequately with nonopioid analgesia.

During a 12-week period, 309 participants received a dose of up to 400 mg of NKTR-181 twice daily, and 301 received placebo.

In the first study, John Markman, MD, the department of neurosurgery at the University of Rochester School of Medicine and Dentistry, and colleagues reported a statistically significant analgesic effect in patients to NKTR-181 throughout the study period.

At week 12, patients in the NKTR-181 group experienced a reduction pre-treatment pain score 57.1% P = .0003)P = .001).

Furthermore, a greater proportion of patients randomly assigned to NKTR-181 described themselves as improved or very much improved using the Patient Global Impression of Change scale and Medical Outcomes Study Sleep Scale scores. In addition, the NKTR-181 arm demonstrated a statistically significant improvement in sleep quantity, sleep adequacy, sleep problems and sleep disturbance when compared with placebo.

Adverse events were reported in 54.4% of the NKTR-181 group and 49.8% of the placebo group. Participants receiving NKTR-181 reported low occurrences of the somnolence and dizziness commonly associated with opioid therapy. The most frequent adverse events were nausea, constipation and vomiting.

In the second study, Jack Henningfield, PhD, Pinney Associates, and colleagues Clinical Opiate Withdrawal Scale (COWS) and Subjective Opiate Withdrawal Scale (SOWS) .

Researchers wrote that COWS scores suggested mild withdrawal in seven participants in the placebo group and three participants in the NKTR-181 group on day 8; and one participant in the placebo group and four participants in the NKTR-181 group on day 15.

During the first week of randomized treatment, mean SOWS scores in the placebo group increased slightly to a maximum value of 2.7, but mean SOWS scores in subjects to NKTR-181 remained at 1.8 or less.

“Our next step is to review these data with the FDA to move forward to a potential [new drug application] filing,” Doberstein told Healio Family Medicine. “If FDA agrees that our current data set is sufficient for filing, we would submit our NDA filing early in 2018.” – by Janel Miller


Henningfield J, et al. Measuring withdrawal in a phase 3 study of new analgesic, NKTR-181, in subjects with moderate to severe chronic low back pain. Presented at: PAINWeek; Sept. 5-9, 2017; Las Vegas.

Markman J, et al. Efficacy, safety and tolerability of NKTR-181 in patients with moderate to severe chronic low-back pain: A phase 3 study. Presented at: PAINWeek; Sept. 5-9, 2017; Las Vegas.

Disclosure: Healio Family Medicine was unable to confirm researchers’ relevant financial disclosures at the time of publication.