Fab Mab? Look Beyond the Lab.

As we move ahead in the US with more biosimilars being submitted for approval – and for interchangeability – attention must be paid to patient outcomes.

Case in point is research presented at the 2013 ACR/ARHP Annual Meeting that hasn’t as yet received the attention it deserves:

Efficacy and Safety of CT-P13 (Infliximab Biosimilar) over Two Years in Patients with Ankylosing Spondylitis: Comparison Between Continuing with CT-P13 and Switching from Infliximab to CT-P13

Background/Purpose: CT-P13 is an infliximab (INX) biosimilar recently approved by the European Medicine Agency. PLANETAS was a 54-week (wk) randomized double-blind parallel group multicenter Phase I study demonstrating pharmacokinetic equivalence of CT-P13 (5 mg/kg infusion every 8 wks) with INX, in patients (pts) with ankylosing spondylitis (AS) (Park W, ARD 2013;72(S3):516). Here we report results from the extension phase of the Phase I equivalence study, investigating long-term efficacy and safety of extended CT-P13 therapy and switching from INX to CT-P13 in pts with AS.

Methods:

In this open-label extension study, a total of 174/210 pts who completed PLANETAS entered into the extension phase: 88 were continuously treated with CT-P13 (maintenance group) and 86 were switched from INX to CT-P13 (switch group) for 1 additional year.

Results: At wk 54 ASAS20/ASAS40 and ASAS partial remission rates were similar between groups (CT-P13, 70.5%/58.0% and 20.5%; INX, 75.6%/53.5% and 19.8%, respectively). During the extension, ASAS20/ASAS40 rates were similar in the maintenance group (70.1%/57.5% at wk 78 and 80.7%/63.9% at wk 102) and the switch group (77.1%/51.8% at wk 78 and 76.9%/61.5% at wk 102). ASAS partial remission rates were also similar between groups; 21.8% and 21.7% at wk 78, and 27.7% and 28.2% at wk 102, respectively. An overview of the efficacy data are shown in the Table. Anti-drug antibodies (ADA) were comparable between the two groups and positivity was maintained throughout the study (maintenance group, 22.2%, 24.4% and 25.0%; switch group, 26.2%, 31.3% and 30.7%, at wk 54, 78 and 102, respectively). ADA negative pts achieved higher ASAS40 responses (maintenance group, 62.9%/61.5%/66.1%; switch group, 58.1%/60.0%/71.2% at wks 54, 78 and 102, respectively) compared with ADA-positive pts (maintenance group, 38.9%/36.8%/55.0%; switch group, 41.7%/33.3%/45.8% at wks 54, 78 and 102, respectively) with no differences between the maintenance and switch groups. The proportion of pts with ≥1 treatment-emergent adverse event (TEAE) was lower in the maintenance group (48.9%) compared with switch group (71.4%) mainly due to fewer mild and moderate AEs. Serious TEAEs were identical between groups (4 vs 4 pts). Other tolerability and safety outcomes were similar in both groups (Table). TEAEs due to hypersensitivity and infusion-related reactions were similar in both groups (5 pts in maintenance group vs 2 pts in switch group). There was 1 case of TB in each group and 1 report of prostate cancer in the maintenance group (considered unrelated to treatment).

The efficacy data was good. But the safety data is concerning:

Biosimilarity and measurement of efficacy is only one dimension. Attention must be paid to effectiveness relative to real-world patient outcomes data. And that means a much closer pharmacovigilance examination of adverse events for both naïve and switched patients.