Celltrion conducted clinical studies of CT-P13 in rheumatoid arthritis (RA) and ankylosing spondylitis (AS), and is seeking extrapolation of CT-P13 across all seven of Remicade's approved indications including Crohn's disease, pediatric Crohn's disease, ulcerative colitis (UC), pediatric UC, psoriatic arthritis and plaque psoriasis.
In the briefing documents, FDA reviewers said the preclinical, clinical and manufacturing data submitted by Celltrion suggest that it is "highly similar" to Remicade. Agency officials noted that while there were differences in the binding of the Fc regions between Remicade and CT-P13, "it is reasonable to extrapolate conclusions regarding the similar efficacy and safety of CT-P13 and U.S.-licensed Remicade to IBD."
In brief, the FDA recommends approval for all indications mostly based on analytical studies along with some clinical (primarily for RA and AS data). Emphasis on analytics is not surprising based on the FDA biosimilar pathway – but what is interesting (and disturbing) is the absence of available real world data. More on this important patient safety issue shortly.
Infliximab is particularly relevant to the overall conversation regarding indication extrapolation because structural differences have been identified as potentially related to the treatment of inflammatory bowel diseases. The EMA has granted the product full extrapolation including inflammatory bowel diseases, while Health Canada did not, citing uncertainty regarding the clinical impact of observed structural differences.
AdComm members will be asked to discuss the similarity of CT-P13 to Remicade, whether there are clinically meaningful differences between the two mAbs, and whether there are sufficient data to support extrapolation to the approved indications beyond those studied in clinical trials. The panel will vote on whether CT-P13 should be approved as a biosimilar of Remicade for each of the seven indications.
Interestingly, the FDA has will not ask the panel to discuss any of the comparative real world data available that speaks to relevant clinical outcomes. This is particularly disturbing since (on page 11 of the briefing package) the agency FDA made statements on switching (per RA and AS) that would support the safety of a one-time switch from innovator to biosimilar. This is particularly important since Celltrion is NOT seeking interchangeability.
Should “defacto interchangeability” be an acceptable regulatory pathway?
Specifically absent from the FDA AdComm package is data from a study, from Mercy University Hospital, University College Cork, Centre for Gastroenterology, Mercy University Hospital, Cork, Ireland, which studied the clinical impact of both the innovator product (Remicade) and CT-P13, the Celltrion biosimilar. The findings are important. Specifically, the rates of surgery of the groups were significantly different.
80% of biosimilar patients required hospital readmission versus 5% of the Remicade) group. (p=0.00004). 60% of patients in the biosimilar group needed steroid augmentation of standard steroid tapering protocol with 50% requiring multiple increases in steroid dose versus 8% of those patients on Remicaide (p-value = 0.0007). Over the course of 8 weeks, 93% of patients in the biosimilar group had an increase in CRP with 7% remaining unchanged whereas 100% of patients in the Remicade group had a decrease in CRP (p=<0.001).
The study’s conclusion is not ambiguous, “Our results suggest that biosimilars may not be as efficacious as the reference medicine. The results found reflect the ECCO statement position that the use of most biosimilars in IBD will require testing in this particular patient population and cannot be extrapolated from other disease populations."
The complete poster can be found here.
An American College of Rheumatology abstract of CT-P13 data shows important differences between adverse events in patients with rheumatoid arthritis and those with ankylosing spondylitis depending on whether or not they were switched.
The ACR abstract can be found here.
The efficacy data was good. But the safety data is concerning. But the FDA AdComm won’t be discussing this study either.
Biosimilarity and measurement of efficacy is only one dimension. Attention must be paid to effectiveness relative to real-world patient outcomes data. Regulatory sins of omission are dangerous when it comes to the public health.