TABLE 1.

Model Input Parameters for Natural History and Treatment Effects: Base-Case, Lower, and Upper Values and Distributions for Probabilistic Sensitivity Analysis

Model Input Parameters	Base-Case Value	Lower Value	Upper Value	Distribution	References
Model settings
Time horizon	10 years	N/A	N/A	N/A
Discount rate for costs	3.0%	N/A	N/A	N/A
Discount rate for QALYs	3.0%	N/A	N/A	N/A
Markov cycle	1.0 year	N/A	N/A	N/A
Time to assess treatment response	12 weeks	N/A	N/A	N/A	13
Adherence rate for TNF inhibitor class	36.5%	27.4%	41.8%	Beta	41
Adherence rate for IL-17A class	64.5%	58.3%	70.5%	Beta	42
Adherence rate for conventional care	79.5%	63.6%	95.4%	Beta	43
Disease progression
Standardized mortality rate for men with AS	1.63	0.06	0.42	Log-normal	60
Standardized mortality rate for women with AS	1.38	0.41	0.98	Log-normal	60
Treatment effect on BASFI progression of TNF inhibitor class (relative risk)	0.42	0.25	0.70	Log-normal	13
Treatment effect on BASFI progression of IL-17A class (relative risk)	0.153	N/A	N/A	N/A	15, 40
Annual progression rate (BASFI) for conventional care	0.082	N/A	N/A	N/A	13
Annual treatment withdrawal rate for biologics	11.0%	6.7%	15.3%	Beta	13
Time to treatment effect of biologics on disease progression (in years)	4.00	N/A	N/A	N/A
Patient baseline characteristics
Mean age	40.0 years	30.0 years	50.0 years	Normal	13
Gender (% male)	70.0%	N/A	N/A	N/A	13
Mean weight	85.0 kg	70.0 kg	100.0 kg	Normal	61
Mean BASDAI	6.12	N/A	N/A	Correlated normal	13
Mean BASFI	5.28	N/A	N/A	Correlated normal	13
Mean BASDAI for responders in conventional care	4.01	3.89	4.13	Correlated normal	13
Mean BASDAI for nonresponders in conventional care	6.33	6.21	6.45	Correlated normal	13
Mean BASDAI for responders in TNF inhibitor class	4.80	4.68	4.92	Correlated normal	13
Mean BASDAI for nonresponders in TNF inhibitor class	7.08	6.96	7.20	Correlated normal	13
Mean BASDAI for responders in IL-17A class for naive TNF inhibitor	4.80	4.68	4.92	Correlated normal	13
Mean BASDAI for nonresponders in IL-17A class for naive TNF inhibitor	7.08	6.96	7.20	Correlated normal	13
Mean BASFI for responders in conventional care	3.52	3.35	3.69	Correlated normal	13
Mean BASFI for nonresponders in conventional care	5.46	5.29	5.63	Correlated normal	13
Mean BASFI for responders in TNF inhibitor class	4.20	4.03	4.37	Correlated normal	13
Mean BASFI for nonresponders in TNF inhibitor class	6.07	5.90	6.24	Correlated normal	13
Mean BASFI for responders in IL-17A class for naive TNF inhibitor	4.20	4.03	4.37	Correlated normal	13
Mean BASFI for nonresponders in IL-17A class for naive TNF inhibitor	6.07	5.90	6.24	Correlated normal	13
Treatment effects of conventional care after 12 weeks
Overall response rate (BASDAI-50)	9.1%	7.3%	10.9%	Beta	13
Mean change in BASDAI for responders	−2.89	−2.31	−3.47	Correlated normal	13
Mean change in BASDAI for nonresponders	−0.36	−0.29	−0.43	Correlated normal	13
Mean change in BASFI for responders	−1.72	−1.38	−2.06	Correlated normal	13
Mean change in BASFI for nonresponders	−0.04	−0.03	−0.05	Correlated normal	13
Treatment effects of TNF inhibitor class after 12 weeks
Overall response rate (BASDAI-50)	42.0%	33.6%	50.4%	Beta	13
Reduced factor in response rate after failing to respond to a TNF inhibitor	0.90	N/A	N/A	N/A	13
Mean change in BASDAI for responders	−3.86	−3.09	−4.63	Correlated normal	13
Mean change in BASDAI for nonresponders	−1.64	−1.31	−1.97	Correlated normal	13
Mean change in BASFI for responders	−3.08	−2.46	−3.70	Correlated normal	13
Mean change in BASFI for nonresponders	−0.44	−0.35	−0.53	Correlated normal	13
Treatment effects of IL-17A class after 12 weeks
Overall response rate (BASDAI-50) in naive TNF inhibitor	41.5%	33.6%	50.4%	Beta	15, 40
Mean change in BASDAI for responders in naive TNF inhibitor	−4.60	−2.98	−6.22	Correlated normal	15, 40
Mean change in BASDAI for nonresponders in naive TNF inhibitor	−1.01	−0.65	−1.36	Correlated normal	15, 40
Treatment effects of IL-17A class after 12 weeks
Mean change in BASFI for responders in naive TNF inhibitor	−-3.75	−2.29	−5.20	Correlated normal	15, 40
Mean change in BASFI for nonresponders in naive TNF inhibitor	−1.17	−0.72	−1.63	Correlated normal	15, 40
Overall response rate (BASDAI-50) in experienced TNF inhibitor	19.7%	11.5%	31.5%	Beta	15, 40
Mean change in BASDAI for responders in experienced TNF inhibitor	−4.98	−4.00	−5.96	Correlated normal	15, 40
Mean change in BASDAI for nonresponders in experienced TNF inhibitor	−0.94	−0.50	−1.39	Correlated normal	15, 40
Mean change in BASFI for responders in experienced TNF inhibitor	−3.79	−2.31	−5.27	Correlated normal	15, 40
Mean change in BASFI for nonresponders in experienced TNF inhibitor	−0.73	−0.27	−1.18	Correlated normal	15, 40
Treatment-related health care utilization and costs
Percent of gastrointestinal ulcers/bleeding in conventional care with NSAIDs	1.9%	1.2%	2.5%	Beta	65
Percent of serious infection in TNF inhibitors	3.5%	N/A	N/A	N/A	13
Percent of tuberculosis reactivation in TNF inhibitors	2.0%	N/A	N/A	N/A	13
Percent of serious infection and tuberculosis reactivation in IL-17A	0.8%	0.4%	1.2%	N/A	13-17, 40
Average cost of gastrointestinal ulcers/bleeding from conventional care with NSAIDs	$5,150	N/A	N/A	N/A	66
Average cost of serious infection from biologics	$19,072	N/A	N/A	N/A	62
Average cost of tuberculosis treatment	$19,000	N/A	N/A	N/A	63
Cost of tuberculosis screening	$8.25	N/A	N/A	N/A	64
Cost of antinuclear antibodies	$86	N/A	N/A	N/A	64
Cost of double stranded DNA	$124	N/A	N/A	N/A	64
Cost of lab monitoring (CBC, ESR, LFT, CRP)	$187	N/A	N/A	N/A	64
Cost of chest x-ray	$23	N/A	N/A	N/A	64
Cost of physician office visit	$110	N/A	N/A	N/A	64
Adalimumab (40 mg/0.8 mL x 2 prefilled syringes)	$5,174	N/A	N/A	N/A	45
Certolizumab (200 mg/1mL)	$4,327	N/A	N/A	N/A	45
Etanercept (50 mg/1mL)	$1,294	N/A	N/A	N/A	45
Golimumab (50 mg/0.5mL)	$4,809	N/A	N/A	N/A	45
Infliximab (100 mg)	$1,168	N/A	N/A	N/A	45
Secukinumab (150 mg/1mL)	$5,541	N/A	N/A	N/A	45
Ixekizumab (80 mg/1mL)	$5,690	N/A	N/A	N/A	45
Overall treatment cost
Average TNF inhibitor (12-week cost)	$21,913	$17,164	$36,261	Log-normal	45, 64
Average IL-17A antibody (12-week cost)	$34,366	$27,493	$41,240	Log-normal	45, 64
Conventional care (12-week cost)	$743	$595	$892	Log-normal	45, 64
Average TNF inhibitor (annual cost)	$70,864	$56,692	$85,037	Log-normal	45, 64
Average IL-17A antibody (annual cost)	$73,004	$58,403	$87,605	Log-normal	45, 64
Conventional care (annual cost)	$2,130	$1,704	$2,556	Log-normal	45, 64

Notes: All drug costs were based on 2019 wholesale acquisition cost from the online RED BOOK.⁴⁵ All other costs were adjusted to 2019 U.S. dollars based on the Consumer Price Index.

AS = ankylosing spondylitis; BASDAI = Bath Ankylosing Spondylitis Disease Activity Index; BASFI = Bath Ankylosing Spondylitis Functional Index; IL-17A = interleukin-17A monoclonal antibody; N/A = not applicable; NSAID = nonsteroidal anti-inflammatory drug; QALY = quality-adjusted life-year; TNF = tumor necrosis factor.