Mechanism of Action
Abatacept, a selective costimulation modulator, inhibits T cell (T lymphocyte) activation by binding to CD80 and CD86, thereby blocking
interaction with CD28. This interaction provides a costimulatory signal
necessary for full activation of T lymphocytes. Activated T lymphocytes are implicated
in the pathogenesis of RA and are found in the synovium of patients with RA.
In vitro, abatacept decreases T cell proliferation
and inhibits the production of the cytokines TNF alpha (TNFα), interferon-γ,
and interleukin-2. In a rat collagen-induced arthritis model, abatacept suppresses inflammation, decreases anti-collagen antibody production, and reduces antigen specific
production of interferon-γ. The relationship of these biological response
markers to the mechanisms by which ORENCIA exerts its effects in RA is unknown.
Pharmacodynamics
In clinical trials with ORENCIA at doses approximating 10
mg/kg, decreases were observed in serum levels of soluble interleukin-2
receptor (sIL-2R), interleukin-6 (IL-6), rheumatoid factor (RF), C-reactive
protein (CRP), matrix metalloproteinase-3 (MMP3), and TNFα. The relationship
of these biological response markers to the mechanisms by which ORENCIA exerts its
effects in RA is unknown.
Pharmacokinetics
Healthy Adults and Adult RA
The pharmacokinetics of abatacept were studied in healthy adult subjects after
a single 10 mg/kg intravenous infusion and in RA patients after multiple 10
mg/kg intravenous infusions (see Table 3).
Table 3: Pharmacokinetic Parameters (Mean, Range) in Healthy
Subjects and RA Patients After 10 mg/kg Intravenous Infusion(s)
| PK Parameter |
Healthy Subjects
(After 10 mg/kg Single Dose)
n=13 |
RA Patients
(After 10 mg/kg Multiple Dosesa)
n=14 |
| Peak Concentration (Cmax) [mcg/mL] |
292 (175-427) |
295 (171-398) |
| Terminal half-life (t1/2) [days] |
16.7 (12-23) |
13.1 (8-25) |
| Systemic clearance (CL) [mL/h/kg] |
0.23 (0.16-0.30) |
0.22 (0.13-0.47) |
| Volume of distribution (Vss) [L/kg] |
0.09 (0.06-0.13) |
0.07 (0.02-0.13) |
| a Multiple intravenous infusions were administered
at days 1, 15, 30, and monthly thereafter. |
The pharmacokinetics of abatacept in RA patients and healthy subjects appeared
to be comparable. In RA patients, after multiple intravenous infusions, the
pharmacokinetics of abatacept showed proportional increases of Cmax and AUC
over the dose range of 2 mg/kg to 10 mg/kg. At 10 mg/kg, serum concentration
appeared to reach a steady-state by day 60 with a mean (range) trough concentration
of 24 (1 to 66) mcg/mL. No systemic accumulation of abatacept occurred upon
continued repeated treatment with 10 mg/kg at monthly intervals in RA patients.
Population pharmacokinetic analyses in RA patients revealed
that there was a trend toward higher clearance of abatacept with increasing body
weight. Age and gender (when corrected for body weight) did not affect
clearance. Concomitant MTX, NSAIDs, corticosteroids, and TNF blocking agents
did not influence abatacept clearance.
No formal studies were conducted to examine the effects of
either renal or hepatic impairment on the pharmacokinetics of abatacept.
Juvenile Idiopathic Arthritis
In patients 6 to 17 years of age, the mean (range)
steady-state serum peak and trough concentrations of abatacept were 217 (57 to
700) and 11.9 (0.15 to 44.6) mcg/mL. Population pharmacokinetic analyses of the
serum concentration data showed that clearance of abatacept increased with baseline body weight. The estimated mean (range) clearance of abatacept in the juvenile
idiopathic arthritis patients was 0.4 (0.20 to 1.12) mL/h/kg. After accounting
for the effect of body weight, the clearance of abatacept was not related to
age and gender. Concomitant methotrexate, corticosteroids, and NSAIDs were also
shown not to influence abatacept clearance.
Animal Toxicology and/or Pharmacology
A juvenile animal study was conducted in rats dosed with
abatacept from 4 to 94 days of age in which an increase in the incidence of
infections leading to death occurred at all doses compared with controls.
Altered T-cell subsets including increased T-helper cells and reduced
T-regulatory cells were observed. In addition, inhibition of T-cell-dependent
antibody responses (TDAR) was observed. Upon following these animals into
adulthood, lymphocytic inflammation of the thyroid and pancreatic islets was
observed.
In studies of adult mice and monkeys, inhibition of TDAR was
apparent. However, infection and mortality, altered T-helper cells, and
inflammation of thyroid and pancreas were not observed.
Clinical Studies
Adult Rheumatoid Arthritis
The efficacy and safety of ORENCIA were assessed in six
randomized, double-blind, controlled studies (five placebo-controlled and one
active-controlled) in patients ≥ 18 years of age with active RA diagnosed
according to American College of Rheumatology (ACR) criteria. Studies I, II,
III, IV, and VI required patients to have at least 12 tender and 10 swollen
joints at randomization. Study V did not require any specific number of tender
or swollen joints. ORENCIA or placebo treatment was given intravenously at
weeks 0, 2, and 4 and then every 4 weeks thereafter.
Study I evaluated ORENCIA as monotherapy in 122 patients
with active RA who had failed at least one non-biologic DMARD or etanercept. In
Study II and Study III, the efficacy and safety of ORENCIA were assessed in
patients with an inadequate response to MTX and who were continued on their
stable dose of MTX. In Study IV, the efficacy and safety of ORENCIA were assessed
in patients with an inadequate response to a TNF blocking agent, with the TNF
blocking agent discontinued prior to randomization; other DMARDs were
permitted. Study V primarily assessed safety in patients with active RA
requiring additional intervention in spite of current therapy with DMARDs; all
DMARDs used at enrollment were continued. Patients in Study V were not excluded
for comorbid medical conditions. In Study VI, the efficacy and safety of ORENCIA
were assessed in MTX-naive patients with RA of less than 2 years disease
duration. In Study VI, patients previously naive to MTX were randomized to
receive ORENCIA plus MTX or MTX plus placebo.
Study I patients were randomized to receive one of three
doses of ORENCIA (0.5, 2, or 10 mg/kg) or placebo ending at week 8. Study II
patients were randomized to receive ORENCIA 2 or 10 mg/kg or placebo for 12
months. Study III, IV, V, and VI patients were randomized to receive a dose of
ORENCIA based on weight range or placebo for 12 months (Studies III, V, and VI)
or 6 months (Study IV). The dose of ORENCIA was 500 mg for patients weighing
less than 60 kg, 750 mg for patients weighing 60 to 100 kg, and 1000 mg for
patients weighing greater than 100 kg.
Clinical Response
The percent of ORENCIA-treated patients achieving ACR 20,
50, and 70 responses and major clinical response in Studies I, III, IV, and VI
are shown in Table 4. ORENCIA-treated patients had higher ACR 20, 50, and 70
response rates at 6 months compared to placebo-treated patients. Month 6 ACR
response rates in Study II for the 10 mg/kg group were similar to the ORENCIA group
in Study III.
In Studies III and IV, improvement in the ACR 20 response
rate versus placebo was observed within 15 days in some patients and within 29
days versus MTX in Study VI. In Studies II, III, and VI, ACR response rates
were maintained to 12 months in ORENCIA-treated patients. ACR responses were
maintained up to three years in the open-label extension of Study II.
In Study VI, a greater proportion of patients treated with
ORENCIA plus MTX achieved a low level of disease activity as measured by a
DAS28-CRP less than 2.6 at 12 months compared to those treated with MTX plus
placebo (Table 4). Of patients treated with ORENCIA plus MTX who achieved
DAS28-CRP less than 2.6, 54% had no active joints, 17% had one active joint, 7%
had two active joints, and 22% had three or more active joints, where an active
joint was a joint that was rated as tender or swollen or both.
Table 4: Clinical Responses in Controlled Trials
| |
Percentof Patients |
| Inadequate Response to DMARDs |
Inadequate Response to MTX |
Inadequate Response to TNF Blocking Agent |
MTX-Naive |
| Study I |
Study III |
Study IV |
Study VI |
Response
Rate |
ORNa
n=32 |
PBO
n=32 |
ORNb
+ MTX
n=424 |
PBO
+ MTX
n=214 |
ORNb
+ DMARDs
n=256 |
PBO +
DMARDs
n=133 |
ORNb
+ MTX
n=256 |
PBO
+ MTX
n=253 |
| ACR 20 |
| Month 3 |
53% |
31% |
62%*** |
37% |
46%*** |
18% |
64%* |
53% |
| Month 6 |
NA |
NA |
68%*** |
40% |
50%*** |
20% |
75%** |
62% |
| Month 12 |
NA |
NA |
73%*** |
40% |
NA |
NA |
76%*** |
62% |
| ACR 50 |
| Month 3 |
16% |
6% |
32%*** |
8% |
18%** |
6% |
40%*** |
23% |
| Month 6 |
NA |
NA |
40%*** |
17% |
20%*** |
4% |
53%*** |
38% |
| Month 12 |
NA |
NA |
48%*** |
18% |
NA |
NA |
57%*** |
42% |
| ACR 70 |
| Month 3 |
6% |
0 |
13%*** |
3% |
6%* |
1% |
19%** |
10% |
| Month 6 |
NA |
NA |
20%*** |
7% |
10%** |
2% |
32%** |
20% |
| Month 12 |
NA |
NA |
29%*** |
6% |
NA |
NA |
43%*** |
27% |
| Major Clinical Responsec |
NA |
NA |
14%*** |
2% |
NA |
NA |
27%*** |
12% |
| DAS28-CRP < 2.6d |
| Month 12 |
NA |
NA |
NA |
NA |
NA |
NA |
41%*** |
23% |
* p < 0.05, ORENCIA (ORN) vs placebo (PBO) or MTX.
** p < 0.01, ORENCIA vs placebo or MTX.
*** p < 0.001, ORENCIA vs placebo or MTX.
a 10 mg/kg.
b Dosing based on weight range [see DOSAGE AND ADMINISTRATION].
c Major clinical response is defined as achieving an ACR 70
response for a continuous 6-month period.
d Refer to text for additional description of remaining joint
activity. |
The results of the components of the ACR response criteria for Studies III
and IV are shown in Table 5. In ORENCIA-treated patients, greater improvement
was seen in all ACR response criteria components through 6 and 12 months than
in placebo-treated patients.
Table 5: Components of ACR Response at 6 Months
| |
Inadequate Response to MTX |
Inadequate Response to TNF Blocking |
| Study III |
Agent Study IV |
ORENCIA + MTX
n=424 |
Placebo + MTX
n=214 |
ORENCIA + DMARDs
n=256 |
Placebo + DMARDs
n=133 |
| Component (median) |
Baseline |
Month 6 |
Baseline |
Month 6 |
Baseline |
Month 6 |
Baseline |
Month 6 |
| Number of tender joints (0-68) |
28 |
7*** |
31 |
14 |
30 |
13*** |
31 |
24 |
| Number of swollen joints (0-66) |
19 |
5*** |
20 |
11 |
21 |
10*** |
20 |
14 |
| Paina |
67 |
27*** |
70 |
50 |
73 |
43** |
74 |
64 |
| Patient global assessmenta |
66 |
29*** |
64 |
48 |
71 |
44*** |
73 |
63 |
| Disability indexb |
1.75 |
1.13*** |
1.75 |
1.38 |
1.88 |
1.38*** |
2.00 |
1.75 |
| Physician global assessmenta |
69 |
21*** |
68 |
40 |
71 |
32*** |
69 |
54 |
| CRP (mg/dL) |
2.2 |
0.9*** |
2.1 |
1.8 |
3.4 |
1.3*** |
2.8 |
2.3 |
** p < 0.01, ORENCIA vs placebo, based on mean percent
change from baseline.
*** p < 0.001, ORENCIA vs placebo, based on mean percent change from
baseline.
a Visual analog scale: 0 = best, 100 = worst.
b Health Assessment Questionnaire: 0 = best, 3 = worst; 20
questions; 8 categories: dressing and grooming, arising, eating, walking,
hygiene, reach, grip, and activities. |
The percent of patients achieving the ACR 50 response for Study III by visit
is shown in Figure 1. The time course for the ORENCIA group in Study VI was
similar to that in Study III.
Figure 1: Percent of Patients Achieving ACR 50 Response by
Visit* (Study III)
ORENCIA-treated patients experienced greater improvement
than placebo-treated patients in morning stiffness.
Radiographic Response
In Study III and Study VI, structural joint damage was
assessed radiographically and expressed as change from baseline in the
Genant-modified Total Sharp Score (TSS) and its components, the Erosion Score
(ES) and Joint Space Narrowing (JSN) score. ORENCIA/MTX slowed the progression
of structural damage compared to placebo/MTX after 12 months of treatment as shown
in Table 6.
Table 6: Mean Radiographic Changes in Study IIIa
and Study VIb
| Parameter |
ORENCIA/MTX |
Placebo/MTX |
Differences |
P-valued |
| Study III |
| First Year |
| TSS |
1.07 |
2.43 |
1.36 |
< 0.01 |
| ES |
0.61 |
1.47 |
0.86 |
< 0.01 |
| JSN score |
0.46 |
0.97 |
0.51 |
< 0.01 |
| Second Year |
| TSS |
0.48 |
0.74c |
- |
- |
| ES |
0.23 |
0.22c |
- |
- |
| JSN score |
0.25 |
0.51c |
- |
- |
| Study VI |
| First Year |
| TSS |
0.6 |
1.1 |
0.5 |
0.04 |
a patients with an inadequate response to MTX.
b MTX-naive patients.
c Patients received 1 year of placebo/MTX followed by 1 year
of ORENCIA/MTX.
d Based on a nonparametric ANCOVA model. |
In the open-label extension of Study III, 75% of patients initially randomized
to ORENCIA/MTX and 65% of patients initially randomized to placebo/MTX were
evaluated radiographically at Year 2. As shown in Table 6, progression of structural
damage in ORENCIA/MTX-treated patients was further reduced in the second year
of treatment.
Following 2 years of treatment with ORENCIA/MTX, 51% of
patients had no progression of structural damage as defined by a change in the
TSS of zero or less compared with baseline. Fifty-six percent (56%) of
ORENCIA/MTX-treated patients had no progression during the first year compared
to 45% of placebo/MTX-treated patients. In their second year of treatment with ORENCIA/MTX,
more patients had no progression than in the first year (65% vs 56%).
Physical Function Response and Health-Related Outcomes
Improvement in physical function was measured by the Health
Assessment Questionnaire Disability Index (HAQ-DI). In the HAQ-DI, ORENCIA
demonstrated greater improvement from baseline versus placebo in Studies II-V
and versus MTX in Study VI. The results from Studies II and III are shown in
Table 7. Similar results were observed in Study V compared to placebo and in
Study VI compared to MTX. During the open-label period of Study II, the
improvement in physical function has been maintained for up to 3 years.
Table 7: Mean Improvement from Baseline in Health Assessment
Questionnaire Disability Index (HAQ-DI)
| |
Inadequate Response to Methotrexate |
| Study II |
Study III |
ORENCIAa
+ MTX
(n=115) |
Placebo
+ MTX
(n=119) |
ORENCIAb
+ MTX
(n=422) |
Placebo
+ MTX
(n=212) |
| HAQ Disability Index |
| Baseline (Mean) |
0.98c |
0.97c |
1.69d |
1.69d |
| Mean Improvement |
| Year 1 |
0.40c,*** |
0.15c |
0.66d,*** |
0.37d |
*** p < 0.001, ORENCIA vs placebo.
a 10 mg/kg.
b Dosing based on weight range [see DOSAGE AND ADMINISTRATION].
c Modified Health Assessment Questionnaire: 0 = best, 3 = worst;
8 questions; 8 categories: dressing and grooming, arising, eating, walking,
hygiene, reach, grip, and activities.
d Health Assessment Questionnaire: 0 = best, 3 = worst; 20
questions; 8 categories: dressing and grooming, arising, eating, walking,
hygiene, reach, grip, and activities. |
Health-related quality of life was assessed by the SF-36 questionnaire at 6
months in Studies II, III, and IV and at 12 months in Studies II and III. In
these studies, improvement was observed in the ORENCIA group as compared with
the placebo group in all 8 domains of the SF-36 as well as the Physical Component
Summary (PCS) and the Mental Component Summary (MCS).
Juvenile Idiopathic Arthritis
The safety and efficacy of ORENCIA were assessed in a
three-part study including an open-label extension in children with polyarticular juvenile idiopathic arthritis (JIA). Patients 6 to 17 years of
age (n=190) with moderately to severely active polyarticular JIA who had an
inadequate response to one or more DMARDs, such as MTX or TNF antagonists, were
treated. Patients had a disease duration of approximately 4 years with
moderately to severely active disease at study entry, as determined by baseline
counts of active joints (mean, 16) and joints with loss of motion (mean, 16);
patients had elevated C-reactive protein (CRP) levels (mean, 3.2 mg/dL) and ESR
(mean, 32 mm/h). The patients enrolled had subtypes of JIA that at disease onset included Oligoarticular (16%), Polyarticular (64%; 20% were rheumatoid
factor positive), and Systemic (20%). At study entry, 74% of patients were
receiving MTX (mean dose, 13.2 mg/m² per week) and remained on a stable dose of
MTX (those not receiving MTX did not initiate MTX treatment during the study).
In Period A (open-label, lead-in), patients received 10
mg/kg (maximum 1000 mg per dose) intravenously on days 1, 15, 29, and monthly thereafter.
Response was assessed utilizing the ACR Pediatric 30 definition of improvement,
defined as ≥ 30% improvement in at least 3 of the 6 JIA core set variables
and ≥ 30% worsening in not more than 1 of the 6 JIA core set variables. Patients
demonstrating an ACR Pedi 30 response at the end of Period A were randomized
into the double-blind phase (Period B) and received either ORENCIA or placebo
for 6 months or until disease flare. Disease flare was defined as a ≥ 30%
worsening in at least 3 of the 6 JIA core set variables with ≥ 30%
improvement in not more than 1 of the 6 JIA core set variables; ≥ 2 cm of
worsening of the Physician or Parent Global Assessment was necessary if used as
1 of the 3 JIA core set variables used to define flare, and worsening in ≥ 2
joints was necessary if the number of active joints or joints with limitation
of motion was used as 1 of the 3 JIA core set variables used to define flare.
At the conclusion of Period A, pediatric ACR 30/50/70
responses were 65%, 50%, and 28%, respectively. Pediatric ACR 30 responses were
similar in all subtypes of JIA studied.
During the double-blind randomized withdrawal phase (Period
B), ORENCIA-treated patients experienced significantly fewer disease flares
compared to placebo-treated patients (20% vs 53%); 95% CI of the difference
(15%, 52%). The risk of disease flare among patients continuing on ORENCIA was
less than one third than that for patients withdrawn from ORENCIA treatment (hazard
ratio=0.31, 95% CI [0.16, 0.59]). Among patients who received ORENCIA
throughout the study (Period A, Period B, and the open-label extension Period
C), the proportion of pediatric ACR 30/50/70 responders has remained consistent
for 1 year.
REFERENCES
1. Ries LAG, Eisner MP, Kosary CL, et al. SEER Cancer Statistics
Review, 1975-2001, National Cancer Institute. Bethesda, MD, http://seer.cancer.gov/csr/1975_2001/.
Accessed 2004.
Last updated on RxList: 9/10/2009