Study to Evaluate Maintenance of Sustained Remission of axSpA With CZP Compared to Placebo

Sustained remission was achieved when a participant had an ASDAS less than (<) 1.3 at Week 32 or Week 36 (if ASDAS < 1.3 at Week 32, it must have been < 2.1 at Week 36; if ASDAS < 2.1 at Week 32, it must have been < 1.3 at Week 36) and an ASDAS < 1.3 at Week 48.

Missing data were handled using non-response imputation (NRI) methods.

The ASDAS was calculated as the sum of the following components:

0.121 x Back pain (BASDAI Q2 result) 0.058 x Duration of morning stiffness (BASDAI Q6 result) 0.110 x PGADA (Patient's Global Assessment of Disease Activity) 0.073 x Peripheral pain/swelling (BASDAI Q3 result) 0.579 × (natural logarithm [ln] of the (CRP [mg/L] + 1)) Back pain, PGADA, duration of morning stiffness, peripheral pain/swelling and fatigue were all assessed on a numerical scale (0 to 10 units).

Disease activity was measured by categorical response variables:

• ASDAS-Inactive Disease (ASDAS-ID): ASDAS < 1.3
• ASDAS-Moderate Disease (ASDAS-MD): ASDAS ≥ 1.3, < 2.1
• ASDAS-High Disease activity (ASDAS-HD): ASDAS ≥ 2.1, ≤ 3.5
• ASDAS-very High Disease activity (ASDAS-vHD): ASDAS > 3.5

Missing data were handled using last observation carried forward (LOCF) methods.

The ASDAS was calculated as the sum of the following components:

0.121 x Back pain (BASDAI Q2 result) 0.058 x Duration of morning stiffness (BASDAI Q6 result) 0.110 x PGADA (Patient's Global Assessment of Disease Activity) 0.073 x Peripheral pain/swelling (BASDAI Q3 result) 0.579 × (natural logarithm [ln] of the (CRP [mg/L] + 1)) Back pain, PGADA, duration of morning stiffness, peripheral pain/swelling and fatigue were all assessed on a numerical scale (0 to 10 units).

ASDAS improvement was measured by binary response variables:

• ASDAS-CII: ASDAS reduction (improvement) of ≥ 1.1 relative to Baseline
• ASDAS-MI: ASDAS reduction (improvement) of ≥ 2.0 relative to Baseline

Missing data were handled using non-response imputation (NRI) methods.

For those who met the criteria for flare (see primary efficacy variable), the time to flare was the length in days from randomization in Part B until the visit at which the criteria for flare were met. Participants who discontinued the study without meeting the criteria for flare were counted as experiencing a flare at the time of their last study visit.

The time to flare was analyzed using Kaplan-Meier methods. If Kaplan-Meier Estimate was NA for all estimates then more than 75 % failed to meet the flare condition.

Missing data were handled using non-response imputation (NRI) methods.

The ASDAS was calculated as the sum of the following components:

0.121 x Back pain (BASDAI Q2 result) 0.058 x Duration of morning stiffness (BASDAI Q6 result) 0.110 x PGADA (Patient's Global Assessment of Disease Activity) 0.073 x Peripheral pain/swelling (BASDAI Q3 result) 0.579 × (natural logarithm [ln] of the (CRP [mg/L] + 1)) Back pain, PGADA, duration of morning stiffness, peripheral pain/swelling and fatigue were all assessed on a numerical scale (0 to 10 units).

Disease activity was measured by categorical response variables:

• ASDAS-Inactive Disease (ASDAS-ID): ASDAS < 1.3
• ASDAS-Moderate Disease (ASDAS-MD): ASDAS ≥ 1.3, < 2.1
• ASDAS-High Disease activity (ASDAS-HD): ASDAS ≥ 2.1, ≤ 3.5
• ASDAS-very High Disease activity (ASDAS-vHD): ASDAS > 3.5

The ASDAS was calculated as the sum of the following components:

0.121 x Back pain (BASDAI Q2 result) 0.058 x Duration of morning stiffness (BASDAI Q6 result) 0.110 x PGADA (Patient's Global Assessment of Disease Activity) 0.073 x Peripheral pain/swelling (BASDAI Q3 result) 0.579 × (natural logarithm [ln] of the (CRP [mg/L] + 1)) Back pain, PGADA, duration of morning stiffness, peripheral pain/swelling and fatigue were all assessed on a numerical scale (0 to 10 units).

ASDAS improvement was measured by binary response variables:

• ASDAS-CII: ASDAS reduction (improvement) of ≥ 1.1 relative to Baseline
• ASDAS-MI: ASDAS reduction (improvement) of ≥ 2.0 relative to Baseline

Missing data were handled using non-response imputation (NRI) methods.

The ASAS20 response was defined as an improvement of at least 20 % and absolute improvement of at least 1 unit on a 0 to 10 Numeric Rating Scale (NRS) in at least 3 of the 4 domains: Patient's Global Assessment of Disease Activity (PGADA), Pain assessment (total spinal pain NRS scores), Function (Bath Ankylosing Spondylitis Functional Index (BASFI)), Inflammation (mean of Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) questions 5 and 6 concerning morning stiffness intensity and duration) and absence of deterioration in the potential remaining domain [deterioration was defined as a relative worsening of at least 20 % and an absolute worsening of at least 1 unit].

Missing data were handled using non-response imputation (NRI) methods.

The ASAS40 response was defined as a relative improvement of at least 40 % and absolute improvement of at least 2 units on a 0 to 10 Numeric Rating Scale (NRS) in at least 3 of the 4 domains: Patient's Global Assessment of Disease Activity (PGADA), Pain assessment (total spinal pain NRS scores), Function (Bath Ankylosing Spondylitis Functional Index (BASFI)), Inflammation (mean of Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) questions 5 and 6 concerning morning stiffness intensity and duration) and no worsening at all in the remaining domain.

Missing data were handled using non-response imputation (NRI) methods.

The ASAS 5/6 response was defined as achieving at least 20 % improvement in 5 of 6 domains, including the 4 domains defined for ASAS20 as well as spinal mobility (lateral spinal flexion) and C-reactive Protein (CRP).

Missing data were handled using non-response imputation (NRI) methods.

The ASAS partial remission (PR) response was defined as a score of ≤ 2 units on a 0 to 10 unit scale in all 4 domains listed for ASAS20.

Missing data were handled using non-response imputation (NRI) methods.

The ASDAS was calculated as the sum of the following components:

0.121 x Back pain (BASDAI Q2 result) 0.058 x Duration of morning stiffness (BASDAI Q6 result) 0.110 x PGADA (Patient's Global Assessment of Disease Activity) 0.073 x Peripheral pain/swelling (BASDAI Q3 result) 0.579 × (natural logarithm [ln] of the (CRP [mg/L] + 1)) Back pain, PGADA, duration of morning stiffness, peripheral pain/swelling and fatigue were all assessed on a numerical scale (0 to 10 units).

There is a minimum score of 0.636 for the total ASDAS score, but no defined upper score. Based on the formula even in the situation that the CRP is normal, any value below 4 is recorded as "below the limit of quantification" (BLQ) and a value of BLQ/2=2 was prespecified. This assumption is triggering the lowest possible value of 0.636.

The change from Part B Baseline is calculated, a negative value indicating improvement and a positive value worsening.

The BASDAI is a validated self-reported instrument, which consists of six 10 unit horizontal Numeric Rating Scales (NRS) to measure the disease activity of ankylosing spondylitis (AS) from the subject's perspective. It measures the severity of fatigue, spinal and peripheral joint pain and swelling, enthesitis, and morning stiffness (both severity and duration) over the last week. The final BASDAI scores ranges from 0 to 10, with lower scores indicating lower disease activity.

The change from Part B Baseline is calculated, a negative value indicating improvement and a positive value worsening.

The BASFI is a validated disease-specific instrument for assessing physical function. The BASFI comprises 10 items relating to the past week. The BASFI is the mean of the 10 scores such that the total score ranges from 0 (Easy) to 10 (Impossible), with lower scores indicating better physical function.

The change from Part B Baseline is calculated, a negative value indicating improvement and a positive value worsening.

The BASMI is a disease-specific measure consisting of 5 clinical measures to reflect subject axial status: cervical rotation; tragus to wall distance; lateral lumbar flexion; lumbar flexion (modified Schober test); intermalleolar distance. According to the linear definition of the BASMI a score of 0 to 10 was calculated for each item based on the measurement. The mean of the sum of the 5 scores provided the total BASMI score, ranging from 0 to 10. The higher the BASMI score the more severe the patient's limitation of movement due to their axial spondyloarthritis (axSpA).

The change from Part B Baseline is calculated, a negative value indicating improvement and a positive value worsening.

The BASDAI50 response was defined as an improvement of at least 50 % in the BASDAI score relative to Baseline.

Missing data were handled using non-response imputation (NRI) methods.

The SPARCC scoring method for lesions found on the Magnetic Resonance Imaging (MRI) is based on an abnormal increased signal on the Short-Tau-Inversion Recovery (STIR) sequence, representing bone marrow edema. Total Sacroiliac (SI) joint SPARCC score can range from 0 to 72 with higher scores indicating higher joint inflammation.

The change from Part B Baseline is calculated, a negative value indicating improvement and a positive value worsening.

The Berlin modification of the ASspiMRI-a is a scoring system with a concentration on Short-Tau-Inversion Recovery (STIR) sequences without other fat saturation techniques. It quantifies changes in 23 Vertebral Units (VU) of the spine. Active inflammation was scored by grading the degree of bone marrow edema from 0 to 3 in 1 dimension on 1 or more consecutive slices that represent the highest level of inflammation in a particular VU.

The change from Part B Baseline is calculated, a negative value indicating improvement and a positive value worsening.

The ASDAS was calculated as the sum of the following components:

0.121 x Back pain (BASDAI Q2 result) 0.058 x Duration of morning stiffness (BASDAI Q6 result) 0.110 x PGADA (Patient's Global Assessment of Disease Activity) 0.073 x Peripheral pain/swelling (BASDAI Q3 result) 0.579 × (natural logarithm [ln] of the (CRP [mg/L] + 1)) Back pain, PGADA, duration of morning stiffness, peripheral pain/swelling and fatigue were all assessed on a numerical scale (0 to 10 units).

Disease activity was measured by categorical response variables:

• ASDAS-Inactive Disease (ASDAS-ID): ASDAS < 1.3
• ASDAS-Moderate Disease (ASDAS-MD): ASDAS ≥ 1.3, < 2.1
• ASDAS-High Disease activity (ASDAS-HD): ASDAS ≥ 2.1, ≤ 3.5
• ASDAS-very High Disease activity (ASDAS-vHD): ASDAS > 3.5

The ASDAS was calculated as the sum of the following components:

0.121 x Back pain (BASDAI Q2 result) 0.058 x Duration of morning stiffness (BASDAI Q6 result) 0.110 x PGADA (Patient's Global Assessment of Disease Activity) 0.073 x Peripheral pain/swelling (BASDAI Q3 result) 0.579 × (natural logarithm [ln] of the (CRP [mg/L] + 1)) Back pain, PGADA, duration of morning stiffness, peripheral pain/swelling and fatigue were all assessed on a numerical scale (0 to 10 units).

ASDAS improvement was measured by binary response variables:

• ASDAS-CII: ASDAS reduction (improvement) of ≥ 1.1 relative to Baseline
• ASDAS-MI: ASDAS reduction (improvement) of ≥ 2.0 relative to Baseline

The ASAS20 response was defined as an improvement of at least 20 % and absolute improvement of at least 1 unit on a 0 to 10 Numeric Rating Scale (NRS) in at least 3 of the 4 domains: Patient's Global Assessment of Disease Activity (PGADA), Pain assessment (total spinal pain NRS scores), Function (Bath Ankylosing Spondylitis Functional Index (BASFI)), Inflammation (mean of Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) questions 5 and 6 concerning morning stiffness intensity and duration) and absence of deterioration in the potential remaining domain [deterioration was defined as a relative worsening of at least 20% and an absolute worsening of at least 1 unit].

The ASAS40 response was defined as a relative improvement of at least 40 % and absolute improvement of at least 2 units on a 0 to 10 Numeric Rating Scale (NRS) in at least 3 of the 4 domains: Patient's Global Assessment of Disease Activity (PGADA), Pain assessment (total spinal pain NRS scores), Function (Bath Ankylosing Spondylitis Functional Index (BASFI)), Inflammation (mean of Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) questions 5 and 6 concerning morning stiffness intensity and duration) and no worsening at all in the remaining domain.

The ASAS 5/6 response was defined as achieving at least 20 % improvement in 5 of 6 domains, including the 4 domains defined for ASAS20 as well as spinal mobility (lateral spinal flexion) and C-reactive Protein (CRP).

The ASAS partial remission (PR) response was defined as a score of ≤ 2 units on a 0 to 10 unit scale in all 4 domains listed for ASAS20.

The ASDAS was calculated as the sum of the following components:

0.121 x Back pain (BASDAI Q2 result) 0.058 x Duration of morning stiffness (BASDAI Q6 result) 0.110 x PGADA (Patient's Global Assessment of Disease Activity) 0.073 x Peripheral pain/swelling (BASDAI Q3 result) 0.579 × (natural logarithm [ln] of the (CRP [mg/L] + 1)) Back pain, PGADA, duration of morning stiffness, peripheral pain/swelling and fatigue were all assessed on a numerical scale (0 to 10 units).

There is a minimum score of 0.636 for the total ASDAS score, but no defined upper score. Based on the formula even in the situation that the CRP is normal, any value below 4 is recorded as "below the limit of quantification" (BLQ) and a value of BLQ/2=2 was prespecified. This assumption is triggering the lowest possible value of 0.636.

The change from Part B Baseline is calculated, a negative value indicating improvement and a positive value worsening.

The BASDAI is a validated self-reported instrument, which consists of six 10 unit horizontal Numeric Rating Scales (NRS) to measure the disease activity of ankylosing spondylitis (AS) from the subject's perspective. It measures the severity of fatigue, spinal and peripheral joint pain and swelling, enthesitis, and morning stiffness (both severity and duration) over the last week. The final BASDAI scores ranges from 0 to 10, with lower scores indicating lower disease activity.

The change from flare Baseline is calculated, a negative value indicating improvement and a positive value worsening.

The BASFI is a validated disease-specific instrument for assessing physical function. The BASFI comprises 10 items relating to the past week. The BASFI is the mean of the 10 scores such that the total score ranges from 0 (Easy) to 10 (Impossible), with lower scores indicating better physical function.

The change from flare Baseline is calculated, a negative value indicating improvement and a positive value worsening.

The BASMI is a disease-specific measure consisting of 5 clinical measures to reflect subject axial status: cervical rotation; tragus to wall distance; lateral lumbar flexion; lumbar flexion (modified Schober test); intermalleolar distance. According to the linear definition of the BASMI a score of 0 to 10 was calculated for each item based on the measurement. The mean of the sum of the 5 scores provided the total BASMI score, ranging from 0 to 10. The higher the BASMI score the more severe the patient's limitation of movement due to their axial spondyloarthritis (axSpA).

The change from flare Baseline is calculated, a negative value indicating improvement and a positive value worsening.

The SPARCC scoring method for lesions found on the Magnetic Resonance Imaging (MRI) is based on an abnormal increased signal on the Short-Tau-Inversion Recovery (STIR) sequence, representing bone marrow edema. Total Sacroiliac (SI) joint SPARCC score can range from 0 to 72 with higher scores indicating higher joint inflammation.

The change from flare Baseline is calculated, a negative value indicating improvement and a positive value worsening.

The Berlin modification of the ASspiMRI-a is a scoring system with a concentration on Short-Tau-Inversion Recovery (STIR) sequences without other fat saturation techniques. It quantifies changes in 23 Vertebral Units (VU) of the spine. Active inflammation was scored by grading the degree of bone marrow edema from 0 to 3 in 1 dimension on 1 or more consecutive slices that represent the highest level of inflammation in a particular VU.

The change from flare Baseline is calculated, a negative value indicating improvement and a positive value worsening.

CZP plasma concentration was measured in micrograms per milliliter (μg/mL). Blood sample measurements that were deemed to be below the level of quantification, were set to half the lower level of quantification (LLOQ) for analysis purposes. Summary statistics were only displayed if at least two-thirds of the values were above the LLOQ and if n was greater or equal to (>=) 4.

The primary purpose of the study was to evaluate treatment options for axSpA patients after being in sustained remission. Hence, one of the objectives was to evaluate the PK of these patients. The CZP plasma concentration of the patients that did not reach sustained remission were therefore not analysed, and the Pharmacokinetic Set A as described in the protocol was removed from the SAP.

Treatment emergent ADAb status positive was defined as either baseline ADAb negative subjects having at least one ADAb confirmed positive sample post baseline or baseline ADAb positive subjects with at least one post baseline sample with >= minimum significant ratio (MSR) increase from baseline on CZP treatment. Once determined positive, the highest titer during Part A and Part B (including Escape and Safety Follow up) was used to categorize the subject.

The primary purpose of the study was to evaluate treatment options for axSpA patients after being in sustained remission. Hence, one of the objectives was to evaluate the immunogenicity of these patients. The ADAb titer of the patients that did not reach sustained remission were therefore not analysed, and the Pharmacokinetic Set A as described in the protocol was removed from the SAP.

An AE was any untoward medical occurrence in a patient or clinical investigation study participant administered a pharmaceutical product that did not necessarily have a causal relationship with this treatment. An AE could therefore have been any unfavorable and unintended sign (including an abnormal laboratory finding), symptom, or disease temporally associated with the use of a medicinal (investigational) product, whether or not related to the medicinal (investigational) product.

An AE was any untoward medical occurrence in a patient or clinical investigation study participant administered a pharmaceutical product that did not necessarily have a causal relationship with this treatment. An AE could therefore have been any unfavorable and unintended sign (including an abnormal laboratory finding), symptom, or disease temporally associated with the use of a medicinal (investigational) product, whether or not related to the medicinal (investigational) product.

For subjects with flare in Part B and do escape to CZP full-dose therapy, only TEAEs with an onset date prior to the start date of escape CZP full-dose therapy were included.

An AE was any untoward medical occurrence in a patient or clinical investigation study participant administered a pharmaceutical product that did not necessarily have a causal relationship with this treatment. An AE could therefore have been any unfavorable and unintended sign (including an abnormal laboratory finding), symptom, or disease temporally associated with the use of a medicinal (investigational) product, whether or not related to the medicinal (investigational) product.

For subjects with flare in Part B and do escape to CZP full-dose therapy, only TEAEs with an onset date after or on the start date of escape CZP full-dose therapy were included.