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).

Conclusion:

CT-P13 was safe and efficacious over 2 years in pts with AS. Switching from INX to CT-P13 was efficacious and tolerable from wk 54 to wk 102. The comparable efficacy and tolerability profiles of CT-P13 and INX in pts with AS observed at wk 54 were maintained up to 102 wks in both groups with continued CT-P13 treatment in the extension study.

Efficacy outcome		CT-P13 throughout study (N=88)	Switched from INX to CT-P13 in extension phase (N=86)
ASAS20, n (%)	Wk 54	62 (70.5)	65 (75.6)
	Wk 78	61 (70.1)	64 (77.1)
	Wk 102	67 (80.7)	60 (76.9)
ASAS40, n (%)	Wk 54	51 (58.0)	46 (53.5)
	Wk 78	50 (57.5)	43 (51.8)
	Wk 102	53 (63.9)	48 (61.5)
ASAS partial remission, n (%)	Wk 54	18 (20.5)	17 (19.8)
	Wk 78	19 (21.8)	18 (21.7)
	Wk 102	23 (27.7)	22 (28.2)
ASDAS-CRP	Baseline (BL)	3.86	3.85
	Mean Δ from BL at Wk 54	−1.77	−1.74
	Mean Δ from BL at Wk 78	−1.88	−1.68
	Mean Δ from BL at Wk 102	−2.03	−1.81
Safety outcome		CT-P13 throughout study (N=90)	Switched from INX to CT-P13 in extension phase (N=84)
TEAEs, n		103	162
pts with ≥1 TEAE, n (%)		44 (48.9)	60 (71.4)
Mild		20 (22.2)	27 (32.1)
Moderate		21 (23.3)	28 (33.3)
Severe		3 (3.3)	5 (6.0)
pts with ≥1 TESAE, n (%)		4 (4.4)	4 (4.8)
pts with ≥1 infection, n (%)		23 (25.6)	29 (34.5)
ADA positive, n (%)	Wk 54	20 (22.2)	22 (26.2)
	Wk 78	21 (24.4)	25 (31.3)
	Wk 102	21 (25.0)	23 (30.7)
ADA, anti-drug antibodies; ASAS, Assessment of SpondyloArthritis international Society; ASDAS-CRP, Ankylosing Spondylitis Disease Activity Score C-reactive protein; TEAE, treatment-emergent adverse event; TESAE, treatment-emergent serious adverse event

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/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/