Interleukin-23 inhibition shows stellar responses.
These long-term, open-label extensions of previously reported phase 3, randomized, double-blind clinical trials provided evidence of multiple advantages for IL-23 inhibition. The story was similar for both agents: After 2 years of use in the extension studies, the two biologics demonstrated stellar treatment response rates that would have been unimaginable only a few years ago, maintenance of efficacy without drop-off over time, exceedingly low dropout rates, and a safety picture that remains reassuring as experience accumulates. Also, the subcutaneously administered IL-23 inhibitors are attractive from a patient convenience standpoint in that maintenance guselkumab is dosed at 100 mg once every 8 weeks, and tildrakizumab is given once every 12 weeks.
Still, there are differences between the two drugs, most notably in apparent effectiveness. While more than half of guselkumab-treated patients had a Psoriasis Area Severity Index (PASI) 100 response--that is, totally clear skin--at 2 years, that was the case for only one-quarter to one-third of patients on tildrakizumab.
Guselkumab (Tremfya) was approved by the Food and Drug Administration in July 2017 for treatment of adults with moderate to severe plaque psoriasis. Tildrakizumab remains investigational.
The 2-year, open-label extension of the phase 3 VOYAGE 1 trial included 735 patients who were either on guselkumab continuously, crossed from adalimumab (Humira) to guselkumab after 48 weeks, or switched from placebo after 16 weeks.
Regardless of their initial treatment arm, patients ended up with similar response rates at 2 years, according to Andrew Blauvelt, MD, who presented the results at the meeting. For example, 2-year PASI 90 response rates in the three groups were 81%-82%. For patients on the IL-23 blocker for the full 2 years, the PASI 90 rate was close to 80% after the first couple of doses, 80% at 1 year, and 82% at 2 years; these rates reflect a flat, sustained response from the first few weeks onward. For those initially on adalimumab, the PASI 90 rate at 1 year was 51%, but after patients switched to guselkumab, that rate rose to 81% at 2 years.
PASI 100 rates at 2 years were 49%-55% in the three patient groups. Of the patients in these groups, 54%-59% achieved an Investigator's Global Assessment (IGA) score of 0. IGA scores of 0 or 1, meaning clear or almost clear skin, were present in 82%-85% of patients at 2 years.
"Dropout rate is an important consideration in long-term studies," observed Dr. Blauvelt, a dermatologist and president of Oregon Medical Research Center in Portland. "For patients on continuous guselkumab there was a 6% dropout rate in the first year and 6% in the second year, so 88% of patients that started guselkumab were still on guselkumab 2 years later. That's impressive. In the other two groups, the dropout rate was 2% per year."
A Dermatology Life Quality Index (DLQI) score of 0 or 1, meaning no disease effects on quality of life, was recorded in 62.5% of the continuous guselkumab group at 48 weeks and 71.1% at 2 years.
"The interesting thing here is that, even though the efficacy numbers are fairly constant between year 1 and year 2, the DLQI goes up and up. Surprising? Maybe not. I think it shows patients are getting happier and happier over time with their disease control," Dr. Blauvelt continued.
Rates of serious adverse events remained low and stable, with no negative surprises during year 2. The serious infection rate was 1.02 cases/100 patient-years in year 1 and 0.84 cases/100 patient-years in year 2. No cases of tuberculosis, opportunistic infections, or serious hypersensitivity reactions occurred during 2 years of treatment.
Two-year results from the ongoing 5-year extension of the phase 3 reSURFACE 1 and reSURFACE 2 trials were presented by Kim A. Papp, MD, PhD, president of Probity Medical Research, Waterloo, Ont. This presentation of 2-year outcomes for 1,237 study participants was a feat, considering that the 12-week results of the trials had been published less than 3 months earlier (Lancet. 2017 Jul 15;390:276-88).
Treatment response rates were closely similar regardless of whether patients were randomized to 100 mg or 200 mg of tildrakizumab every 12 weeks. The overall 2-year PASI 75 rates were 81%84%, with PASI 90 responses of 52%-61% and PASI 100 rates of 22%-34% across the two trials, which were analyzed separately for this presentation.
"I think these data are very compelling that the loss of response over time is minimal," according to the dermatologist. "We've also seen that safety over 2 years has no surprises; in fact, it's remarkably quiet. The rate of severe infections, which is important to look at for any treatment suppressing the immune system, is low and occurs almost independent of dose, which is very hopeful. It's a promising sign."
Indeed, the serious infection rate was 0.8 cases/100 patient-years regardless of whether subjects were on tildrakizumab at 100 mg or 200 mg.
Controversy over how to report long-term outcomes
A hot topic among clinical trialists in dermatology concerns how to report study results. The traditional method in studies funded by pharmaceutical companies is known as the "last observation carried forward" analysis. It casts the study drug results in the most favorable possible light because, when a subject drops out of a trial for any reason, their last measured value for response to treatment is carried forward as though the patient completed the study. Thus, psoriasis patients who drop out because they couldn't tolerate a therapy or developed a serious side effect dictating discontinuation will be scored on the basis of their last PASI response, creating a bias in favor of active treatment.
A more conservative analytic method is known as the "nonresponder imputation" analysis. By this method, a patient who drops out of a trial is automatically categorized as a treatment failure, even if the reason was that the patient moved and could no longer make visits to the study center.
The prespecified guselkumab analysis presented by Dr. Blauvelt involved nonresponder imputation through year 1 and imputation based on the reason for discontinuation in the second year. In contrast, the 2-year tildrakizumab analysis presented by Dr. Papp used the far more common last observation carried forward method.
To help the audience appreciate the importance of looking at the analytic methods used in a studies and help them understand the clinical significance of the results, Dr. Blauvelt provided a reanalysis of the 2-year guselkumab data using the last observation carried forward method. Across the board, the numbers became more favorable. For example, the PASI 75 rate of 95.7% using the prespecified nonresponder imputation analysis crept up to 96.8% under the last observation carried forward method; for comparison, the PASI 75 rates were 81%-84% in the tildrakizumab analysis.
"If you wanted to compare apples to apples with some other drugs, you would use these numbers --the as-observed analysis numbers used by most other companies with other drugs. If you wanted to determine what the true-life numbers are, they'd probably be something between the non-responder imputation and as-observed numbers," said to Dr. Blauvelt.
Dr. Papp was untroubled by the use of the last observation carried forward method in the particular case of the tildrakizumab long-term extension study.
"There is reason to believe the as-observed analysis doesn't affect the integrity of the data because the dropout rate is extraordinarily low," he said.
The guselkumab analysis was sponsored by Janssen Pharmaceutica; the tildrakizumab analysis was sponsored by Merck and by Sun Pharma. Dr. Blauvelt and Dr. Papp were paid investigators in both studies and serve as scientific advisers to virtually all companies invested in the psoriasis therapy developmental pipeline.
BY BRUCE JANCIN
EXPERT ANALYSIS FROM THE EADV CONGRESS
Please Note: Illustration(s) are not available due to copyright restrictions.
Caption: Dr. Blauvelt
Caption: Dr. Papp
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|Date:||Feb 1, 2018|
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