A sub-study of a clinical trial comparing the adalimumab biosimilar PF-06410293 (Pfizer; Abrilada US, Amsparity EU) to the EU reference product (Humira) in rheumatoid arthritis (RA) evaluated the usability of prefilled pens (PFP) by patients and their caregivers.

The study was published in Rheumatology and Therapy and demonstrated that patients with RA and their caregivers can safety and effectively administer the biosimilar using a PFP.

The authors noted previous studies had shown that Humira autoinjector pens are “suitable” and “generally preferred by patients due to their ease of use and convenience.”

Adalimumab is a monoclonal antibody to tumor necrosis factor (TNF) alpha. The reference product has been marketed in the United States and European Union since 2002 and 2003 to treat RA and is approved for multiple other indications.

The investigators evaluated injection success by patients and their caregivers in administering the biosimilar via PFP, based on assessments by the patients and staff at the study site. The sub-study took place during an open-label treatment period in a phase 3 trial comparing the biosimilar adalimumab to its EU reference product and included 49 adult patients with active RA not adequately controlled with methotrexate.

Prior to the sub-study, the patients had been randomized 1:1 to receive the biosimilar or reference product, which was administered via prefilled syringe (PFS). At week 26, the patients on the reference product were re-randomized to continue or switch to the biosimilar. At week 52, the start of the sub-study, the remaining patients in the reference product group were switched to the biosimilar.

The patients received 2 doses of the biosimilar via PFS at weeks 52 and 54, and then received 6 additional biweekly doses via the PFP device. The study site personnel trained patients or their caregivers to administer the biosimilar using the device; none of the patients had received an injection via an autoinjector or injection pen prior to the sub-study. All injections were given by patients or their caregivers, with doses alternating between the study site and home.

The primary endpoint of the study was the delivery system success rate (DSSR): the percentage of participants who successfully delivered each of the 6 attempted injections with the PFP device.

The success of home-administered injections were assessed by the patient or caregiver, and the devices were later inspected by study staff to confirm full injection volume was delivered. The success of study site-administered injections was assessed by study personnel who observed the injections. After administering over 294 total injections, the DSSR was 100% (95% confidence interval 92.0-100%), and “complete injection was confirmed following inspection of 292 used and returned PFPs.”

The authors noted that safety indicators will be reported along with the main study results, and there were no additional safety assessments conducted for the PFP sub-study. However, the adverse events reported in the sub-study population “were consistent with those reported for the first year of the overall study population.”

They added that there were no medical device complaints, and “47/49 (95.9%) participants who completed the sub-study elected to continue study treatment using PFP injections, rather than switching back to the PFS.”

The investigators concluded “all actual PFP users could safely and effectively administer ADL-PF by PFP at each visit, and nearly all participants who completed the sub-study elected to continue study treatment using PFP injections.”

Reference

Fleischmann RM, Bock AE, Zhang W, et al. Usability study of PF-06410293, an adalimumab biosimilar, by prefilled pen: Open-label, single-arm, sub-study of a phase 3 trial in patients with rheumatoid arthritis. Rheumatol Ther. Published online, March 18, 2022. doi:10.1007/s40744-022-00439-8.

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