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Chemokine receptor CCR1 antagonist CCX354-C treatment for rheumatoid arthritis: CARAT-2, a randomised, placebo controlled clinical trial
  1. Paul P Tak1,
  2. Andra Balanescu2,
  3. Vira Tseluyko3,
  4. Silvia Bojin4,
  5. Edit Drescher5,
  6. Dan Dairaghi6,
  7. Shichang Miao6,
  8. Vittorio Marchesin6,
  9. Juan Jaen6,
  10. Thomas J Schall6,
  11. Pirow Bekker6
  1. 1Clinical Immunology and Rheumatology, F4-105, AMC/University of Amsterdam, Amsterdam, The Netherlands (currently also at GlaxoSmithKline, Stevenage, UK)
  2. 2Internal Medicine and Rheumatology, St Maria Hospital, Bucharest, Romania
  3. 3City Clinical Hospital, Kharkiv, Ukraine
  4. 4Spitalul Judetean de Urgenta ‘Dr Fogolyan Kristof’, Sf Gheorghe, Romania
  5. 5Veszprém Megyei Csolnoky Ferenc Kórház Nonprofit Zrt, Veszprém, Hungary
  6. 6ChemoCentryx, Inc, Mountain View, California, USA
  1. Correspondence to Paul P Tak, AMC/University of Amsterdam, Clinical Immunology and Rheumatology, F4-105, PO Box 22700, Amsterdam 1100 DD, Netherlands; p.p.tak{at}amc.uva.nl

Abstract

Objectives CCX354-C is a specific, orally administered antagonist of the C-C chemokine receptor 1, which regulates migration of monocytes and macrophages to synovial tissue. This clinical trial evaluated the safety and efficacy of CCX354-C in patients with rheumatoid arthritis (RA).

Methods CARAT-2 is a 12-week double-blind, randomised, placebo controlled trial in 160 patients with RA, with 68 tender joint count and 66 swollen joint count ≥8 and C-reactive protein (CRP) >5 mg/l, despite being on methotrexate for at least 16 weeks. Subjects received placebo, CCX354-C 100 mg twice daily, or 200 mg once daily for 12 weeks. Endpoints included safety (primary) and RA disease activity assessments based on American College of Rheumatology (ACR) response, and changes in 28-joint disease activity score–CRP, individual ACR components, as well as soluble bone turnover markers.

Results CCX354-C was generally well tolerated by study subjects. The ACR20 response at week 12 was 39% in the placebo group, 43% in the 100 mg twice daily group (difference and 95% CI compared with placebo, 4.5 (−14.1 to 23.1); p=0.62) and 52% in the 200 mg once daily group (13.0 (−5.8 to 31.8); p=0.17) in the intention-to-treat population, and 30% in the placebo group, 44% in the 100 mg twice daily group (14.4 (−5.9 to 34.8); p=0.17), and 56% in the 200 mg once daily group (25.8 (5.3 to 46.4); p=0.01) in the prespecified population of patients satisfying CRP and joint count eligibility criteria at the screening and day 1 (predose) visits.

Conclusions CCX354-C exhibited a good safety and tolerability profile and evidence of clinical activity in RA.

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Macrophages and certain T cells are sources of pro-inflammatory cytokines such as tumour necrosis factor α, interleukin 1 and interleukin 6, and cause joint destruction.1,,3 High levels of C-C chemokine receptor 1 (CCR1)-expressing macrophages and CCR1 chemokines such as CCL3, CCL5 and CCL15 have been identified in inflamed rheumatoid arthritis (RA) synovial fluid and tissue.4,,7 RA synovial fluid contains proteolytically processed forms of chemokines with markedly enhanced activity towards CCR1.8 In-vitro migration studies have shown that CCR1-mediated RA monocyte migration induced by RA synovial fluid can be blocked with either a CCR1 blocking antibody or a small molecule CCR1 antagonist, in contrast to findings with CCR2 or CCR5 inhibitors.9 CCR1 and its ligands are also involved in osteoclast maturation, motility and activation.10,,12

CCX354-C is a small molecule CCR1 antagonist that inhibits CCR1-dependent signalling, including chemotaxis.13 Early clinical studies indicated that orally administered CCX354-C was well tolerated with a pharmacokinetic profile suitable for once or twice daily oral administration.13 These early clinical trials included CCR1 Antagonist Rheumatoid Arthritis Trial 1 (CARAT-1), a phase 1/2 clinical trial to assess the safety and tolerability of CCX354-C in 24 subjects with stable RA on methotrexate. The current clinical trial, CCR1 Antagonist Rheumatoid Arthritis Trial 2 (CARAT-2), is a phase 2 clinical trial of the safety and efficacy of CCX354-C in subjects with RA.

Methods

This clinical trial was designed by ChemoCentryx, Inc. All study procedures were governed by International Conference on Harmonisation Good Clinical Practice standards. Each study centre obtained ethics committee approval for the trial before the enrolment of any study subjects. Trial conduct and data collection were subcontracted to Kendle International Inc. The authors, together with Kendle biostatisticians, analysed the data and prepared the manuscript, and vouch for the veracity and completeness of the data and analysis.

Study subjects

Forty-four study centres in eight countries in Europe enrolled subjects from August 2010 to July 2011. Adult subjects with moderate to severe RA, despite being on 7.5–25 mg per week of methotrexate for at least 16 weeks and on a stable dose for at least 8 weeks before randomisation, were eligible. Subjects had to continue taking their regular methotrexate dose in addition to study treatment over the course of the study. All subjects were required to take supplemental folic or folinic acid (≥5 mg per week) during the clinical trial. Subjects had to have at least eight tender joints (of 68 total joints)14 and at least eight swollen joints (of 66 total joints)14 and serum C-reactive protein (CRP) levels above 5 mg/l assessed during the 21-day screening period. CRP was measured at a central laboratory, using the Roche Tina-quant CRP (latex) highly sensitive assay (Roche Diagnostics GmbH, D-68298, Mannheim; upper limit of normal 5 mg/l). The tender joint count (TJC), swollen joint count (SJC) and CRP level were assessed again on day 1, just before the first dose of study medication, to confirm eligibility. However, for practical reasons the day 1 results were not used to exclude subjects from the trial, because subjects started taking study medication on day 1. Subjects receiving glucocorticoids (up to 10 mg prednisone equivalent) had to be on stable doses for at least 4 weeks before randomisation. Excluded drugs were: etanercept or anakinra within 4 weeks; sulfasalazine, azathioprine, 6-mercaptopurine, mycophenolate mofetil, tetracycline, ciclosporin, gold, tacrolimus, sirolimus, other disease-modifying antirheumatic drugs, infliximab, adalimumab, abatacept, certolizumab, golimumab or tocilizumab within 8 weeks; leflunomide within 6 months; and B-cell-depleting agents such as rituximab or ocrelizumab, or cytotoxic agents, such as cyclophosphamide or chlorambucil, within 1 year of randomisation.

Clinical trial design

CARAT-2 was a randomised, double-blind, placebo controlled clinical trial. Subjects were stratified based on previous biological agent use, and based on current glucocorticoid use, and were then randomly assigned to receive placebo, CCX354-C 100 mg twice daily, or 200 mg once daily at a 1:1:1 ratio for 12 weeks, followed by a 4-week observational period off treatment for safety follow-up. The randomisation code was generated by a biostatistician not otherwise involved in the trial. Stratification and randomisation occurred using a centralised interactive voice response system. The daily dose of 200 mg CCX354-C was selected based on the pharmacokinetic, safety and tolerability profiles of CCX354-C in earlier trials. CCX354-C 100 mg twice daily or 200 mg once daily was projected to provide at least 90% CCR1 plasma coverage around the clock.13 To conceal the allocation sequence, placebo and CCX354-C tablets, containing 100 mg CCX354-C, kits (boxes) and bottles were identical in appearance and subjects received one kit with three bottles, each containing 30 tablets of study medication, every 4 weeks. The placebo kits contained three bottles of placebo tablets, the 100 mg twice daily kits contained two bottles of CCX354-C tablets (bottles 1 and 3) and one bottle of placebo (bottle 2), and the 200 mg once daily kits contained two bottles of CCX354-C tablets (bottles 1 and 2) and one bottle of placebo (bottle 3). Subjects were asked to take one tablet from each of the first two bottles every morning and one tablet from the third bottle every evening, 12 h after the morning dose. Study medication was to be taken with water and within 1 h after a meal.

Safety was assessed at all study visits after baseline, weeks 1, 2, 4, 8, 12 and 16. RA disease activity changes, based on American College of Rheumatology (ACR) 20, 50 and 70 response, disease activity score in 28 joints (DAS28)–CRP and ACR components were also assessed at these time points. Soluble bone turnover markers, serum C-telopeptide (CTx; βCrosslaps; Roche), procollagen type I N-terminal propeptide (PINP; immunoassay; Roche, Siemens Healthcare Diagnostics, Tarrytown, NY) and osteocalcin (N-mid immunoassay; Roche), as well as intact parathyroid hormone (iPTH; ADVIA Centaur immunoassay, Siemens Healthcare Diagnostics, Tarrytown, NY) were measured at baseline, weeks 1, 4, 12 and 16. CCX354 was measured in plasma samples obtained at all study visits during the 12-week treatment period using high-performance liquid chromatography with tandem mass spectrometric detection (lower limit of detection 1 ng/ml). The maximum plasma concentration (Cmax) was estimated based on plasma CCX354 measured 1–4 h after dosing, and the trough plasma concentration based on plasma CCX354 measured 11–13 h after 100 mg twice daily and 22–24 h after 200 mg once daily dosing.

Definition of endpoints and statistical analysis

The primary endpoint was safety assessment based on adverse event incidence. Secondary endpoints include efficacy based on ACR responses at week 12, DAS28–CRP, ACR components and soluble bone turnover marker changes.

Study populations of interest include: (1) the intention-to-treat population comprising all subjects who were randomly assigned and had at least one post-baseline DAS28–CRP measurement; (2) the day 1 eligible population, predefined in the study protocol, comprising all subjects meeting CRP and joint count eligibility criteria during screening and day 1 predosing (a total of 31 subjects, 14 in the placebo group, eight in the 100 mg twice daily group and nine in the 200 mg once daily group were excluded from this population because they had CRP levels ≤5 mg/l, or SJC or TJC <8 at the day 1 visit); (3) the biological-naive population who have not previously received biological therapies; and (4) the day 1 eligible, biological-naive population.

No inferential statistical analyses were performed on safety measurements. Categorical efficacy measurements such as ACR20 were analysed by Cochran–Mantel–Haenszel χ2 testing, incorporating the two baseline stratification factors for each pairwise treatment comparison with placebo. For continuous variables, testing was performed using linear contrasts of an analysis of covariance model with treatment group as a factor and baseline DAS28–CRP and the two baseline stratification factors as covariates. All statistical testing was two-sided and Dunnett's adjustment was used to control the type I error rate at α=0.05. For subjects missing DAS28–CRP data at week 12 and other time points of interest, the last post-randomisation observation carried forward method was applied to impute missing data. For binary data such as the ACR20, subjects were considered non-responders at time points with missing data.

With the planned sample size of 50 subjects per treatment group, it was estimated that a difference of 0.8 in DAS28–CRP between any active group and placebo could be detected with statistical power of at least 90%, SD 1.0, type I error 0.025. Furthermore, a difference of approximately 32% in ACR20, ACR50, or ACR70 response could be detected with statistical power of approximately 80%, assuming a placebo ACR20 response rate of 30%, a historically reasonable rate.

Results

Study subjects

Subject disposition is shown in figure 1. Of the 287 subjects screened, 160 were randomly assigned. Most (75%) ineligible subjects had CRP levels below 5 mg/l. Over 82%, 132 of subjects, completed the clinical trial. Demographics and baseline characteristics of the study population are shown in table 1 and were similar across treatment groups.

Figure 1

Subject disposition. Two hundred and eighty seven subjects were screened, of whom 160 were randomly assigned. Screen failure occurred most commonly for low C-reactive protein (75%). Of the 160 subjects, 54 were randomly assigned to placebo, and 53 each to CCX354-C 100 mg twice daily and 200 mg once daily, respectively. In these groups, 83%, 77% and 87% completed the study. The most common reasons for early withdrawal were consent withdrawn (nine subjects), sponsor decision due a study medication importation dispute with customs in the Ukraine (nine subjects) and adverse events (eight subjects). All 160 randomly assigned subjects were included in the intention-to-treat population, except for one subject in the 200 mg once daily group, who was excluded because of lack of data beyond day 1 (baseline). All 160 randomly assigned subjects were included in the safety population; one subject, randomly assigned to receive placebo, accidentally received 200 mg once daily for 4 weeks during the study. Therefore, this subject was included in the 200 mg once daily group for the purpose of safety analyses.

Table 1

Demographics and baseline characteristics of the intention-to-treat population

Safety

Safety results are summarised in table 2. The overall number of subjects reporting adverse events was 26 (49%) in the placebo group, compared with 30 (57%) in the 100 mg twice daily group and 21 (39%) in the 200 mg once daily group. The most common adverse event was headache, reported in four (8%) subjects in the placebo group, compared with three (6%) in the 100 mg twice daily group and six (11%) in the 200 mg once daily group. Other commonly reported adverse events included nasopharyngitis and nausea. Four serious adverse events, not considered to be related to study medication, were observed, all in the 100 mg twice daily group. These include non-cardiac chest pain, syncope due to a vasovagal reaction to blood draw, non-fatal myocardial infarction and temporal lobe epilepsy, which occurred during the 4-week treatment-free follow-up period. Withdrawal from study due to adverse events was reported in nine subjects, two (4%) in the placebo group (one due to nausea and vomiting and another due to RA symptoms), seven (13%) in the 100 mg twice daily group (two due to gastrointestinal symptoms, two due to RA symptoms and one each due to angina, urticaria and toe pain with subungual haemorrhage) and none in the 200 mg once daily group.

Table 2

Adverse events in the safety population

The mean (±SD) change from baseline to week 12 in serum total cholesterol was −0.21 (±0.61), 0.12 (±0.75) and 0.37 (±0.94) mmol/l in the placebo, 100 mg twice daily, and 200 mg once daily groups, respectively. The mean (±SD) change from baseline to week 12 in serum triglyceride levels was 0.04 (±0.69), −0.12 (±0.69) and 0.11 (±0.95) mmol/l in the three groups, respectively. Four subjects had alanine transaminase elevations more than three times the upper limit of normal, one in the placebo group, two in the 100 mg twice daily group and one in the 200 mg once daily group. These abnormalities were not associated with bilirubin changes or clinical abnormalities, and were not considered to be related to study medication. The mean (±SD) white blood cell count at week 12 was 8.4 (±2.7), 8.6 (±2.7) and 7.6 (±2.5)×103/µl in the placebo, 100 mg twice daily and 200 mg once daily groups, respectively, and the mean (±SD) monocyte count at week 12 was 0.50 (±0.16), 0.44 (±0.17) and 0.44 (±0.15)×103/µl in the three groups, respectively. The mean (±SD) systolic/diastolic blood pressure at week 12 was 128 (±12)/78 (±8), 131 (±16)/78 (±9) and 130 (±13)/79 (±9) mm Hg, respectively.

Efficacy

The ACR20, 50 and 70 responses at week 12 are summarised in table 3. The CCX354-C 200 mg once daily group generally had the highest ACR20, 50 and 70 responses compared with placebo. ACR20 responses ranged from 52% to 62%, ACR50 from 29% to 35% and ACR70 from 19% to 24% across various defined subject populations in the 200 mg once daily group, compared with 26% to 39%, 15% to 24% and 9% to 13%, respectively, in the placebo group. Differences in ACR20 response at week 12 between the 200 mg once daily and placebo groups were statistically significant for the day 1 eligible population (p=0.014) and for the day 1 eligible biological-naive population (p=0.002). The CCX354-C 100 mg twice daily group showed numerically but not statistically higher ACR response rates compared with placebo.

Table 3

ACR20, 50 and 70 responses at week 12

DAS28–CRP mean (±SD) changes from baseline to week 12 were −1.36 (±1.04), −1.41 (±1.50) and −1.67 (±1.37) in the placebo, 100 mg twice daily and 200 mg once daily groups, respectively, when day 1 ineligible subjects were included, and −1.26 (±1.14), −1.43 (±1.51) and −1.79 (±1.35) in day 1 eligible subjects. Differences between CCX354-C treatment groups and placebo were not statistically significant for DAS28–CRP. The change from baseline over the course of the study for the ACR components, ie, 68 TJC, 66 SJC, CRP, erythrocyte sedimentation rate, subject assessment of RA, subject assessment of pain, physician assessment of RA and health assessment questionnaire disability index are shown in figure 2. The CCX354-C 200 mg once daily group showed the largest decreases from baseline over the course of the study for most measurements. The change in 68 TJC in the 200 mg once daily group was significantly different (p<0.05) at week 4 (p=0.045) compared with placebo. The change in CRP in the 200 mg once daily group was significantly different at week 12 (p=0.023) compared with placebo. The other changes were numerically superior during the 12-week treatment period, but not statistically different compared with placebo.

Figure 2

American College of Rheumatology component results. The mean (SEM) change from baseline in the placebo (yellow), CCX354-C 100 mg twice daily (blue), and 200 mg once daily (maroon) groups in (A) 68 tender joint count (TJC); (B) 66 swollen joint count (SJC); (C) C-reactive protein (CRP) in milligrams per litre; (D) erythrocyte sedimentation rate (ESR) in millimetres per hour; (E) subject assessment of rheumatoid arthritis (RA) in millimetres, based on a 100 mm visual analogue scale (VAS); (F) subject assessment of pain in millimetres, based on a 100 mm visual analogue scale; (G) physician (MD) assessment of pain in millimetres, based on a visual analogue scale; and (H) health assessment questionnaire disability index (HAQ–DI). Placebo group N=54, 100 mg twice daily N=53; 200 mg once daily N=52. The 12-week treatment period is indicated by a solid blue line above the X axis, and the 4-week study medication-free period by a dotted blue line above the X axis. The asterisks indicate p<0.05 for the CCX354-C 200 mg once daily group compared with placebo based on linear contrasts of an analysis of covariance model with treatment group as a factor and baseline value for each parameter and the two baseline stratification factors as covariates. All statistical testing was two-sided and Dunnett's adjustment was used to control the type I error rate at α=0.05.

The change from baseline in bone turnover markers CTx, osteocalcin and PINP over the course of the study is shown in figure 3. CTx showed a median percentage change from baseline of 16% at week 4 in the 200 mg once daily group (p=0.006 compared with placebo). Both the 200 mg once daily and 100 mg twice daily groups showed decreases from baseline that were significantly different compared with placebo at several time points for these bone markers. iPTH levels did not change significantly in the CCX354-C groups compared with placebo: at week 12, the mean (±SD) iPTH levels were 4.2 (±2.0), 4.5 (±1.9) and 4.4 (±1.6) pmol/l in the placebo, 100 mg twice daily and 200 mg once daily groups, respectively.

Figure 3

Bone turnover marker results. The median percentage change from baseline in the placebo (yellow), CCX354-C 100 mg twice daily (blue), and 200 mg once daily (maroon) groups in (A) serum C-telopeptide; (B) serum osteocalcin and (C) serum procollagen type I N-terminal propeptide (PINP). Placebo group N=54, 100 mg twice daily N=53; 200 mg once daily N=52. The 12-week treatment period is indicated by a solid blue line above the X axis, and the 4-week study medication-free period by a dotted blue line above the X axis. The asterisks indicate p<0.05 (one asterisk) and p<0.01 (two asterisks) for CCX354-C compared with placebo based on the Wilcoxon rank sum test.

Plasma CCX354 results

CCX354 plasma concentration data indicated that the mean (±SD) Cmax was 2727 (±1563) ng/ml in the CCX354-C 200 mg once daily group and 1665 (±643) ng/ml in the CCX354-C 100 mg twice daily group. The trough plasma concentration was 556 (±763) ng/ml in the CCX354-C 200 mg once daily group and 1188 (±601) ng/ml in the 100 mg twice daily group.

As a CCX354 plasma concentration of approximately 100 ng/ml (∼250 nmol/l) was shown to block approximately 90% of Alexa647-MIP-1α binding to CCR1 in ex-vivo assays,13 it was of interest to determine what the clinical response was in subjects who presumably were compliant with taking their study medication, readily absorbed the drug, and therefore consistently had plasma CCX354 levels above 100 ng/ml throughout the trial. Most subjects with plasma CCX354 levels above 100 ng/ml were ACR20 responders at week 12 in both 200 mg once daily and 100 mg twice daily groups, whereas subjects with poor CCX354 plasma exposure were not (figure 4).

Figure 4

American College of Rheumatology 20 (ACR20) response at week 12 by CCX354 plasma exposure. ACR20 response in the two CCX354-C groups based on good CCX354 plasma exposure, defined as plasma CCX354 of at least 100 ng/ml across study visits, or poor CCX354 plasma exposure, defined as plasma CCX354 less than 100 ng/ml for at least one of the study visits, including week 12 or the last available sample. (A) All study subjects, including the day 1 ineligible subjects, and (B) including only day 1 eligible subjects. The asterisks indicate p<0.05 (one asterisk) and p<0.01 (two asterisks) for subjects with good exposure versus poor exposure, based on the two-tailed Fisher's exact test. BID, twice daily; QD, once daily.

Discussion

CCX354-C appeared to be well tolerated in this clinical trial in 160 subjects with moderate to severe residual RA, despite being on methotrexate. No significant safety issues were uncovered that would prevent its further study. The serious adverse events observed were not considered to be related to CCX354-C. There was no apparent increased risk of infections or evidence of a suppressive effect on white blood cells or monocytes. The three cases of alanine transaminase elevations observed in subjects receiving CCX354-C were not considered to be related to CCX354-C. CCX354-C did not appear to affect blood pressure adversely. There was a slight increase in the mean total cholesterol level with CCX354-C treatment. This has been observed commonly with other approved RA therapies, including infliximab, adalimumab and tocilizumab,15 and may be indicative of anti-inflammatory activity. Total cholesterol is decreased under inflammatory conditions, and with effective anti-inflammatory treatment, cholesterol levels are restored. Triglyceride levels did not change with CCX354-C treatment.

Efficacy results showed clinical and biological activity of CCX354-C. The 200 mg once daily dose appeared to be more efficacious than 100 mg twice daily. In particular, there were more ACR20, 50 and 70 responders at week 12 in the CCX354-C 200 mg once daily group compared with the 100 mg twice daily and placebo groups. Subjects naive to biological treatments, who constituted the vast majority of subjects in this trial (88%), responded well to 200 mg once daily CCX354-C, with an ACR20 response of 57–62% (table 3).

CCX354-C 200 mg once daily decreased CRP significantly compared with placebo at week 12. Data from other RA efficacy measures are consistent with a greater treatment effect of CCX354-C 200 mg once daily compared with placebo. TJC, erythrocyte sedimentation rate, DAS28, SJC, subject's assessment of RA and pain and physician assessment of RA all showed numerically greater improvements with CCX354-C 200 mg once daily compared with placebo.

Bone turnover markers CTx, osteocalcin and PINP showed statistically significant treatment effects, evident as early as 1 week, supporting the bone antiresorptive efficacy of CCX354-C in RA. This finding is consistent with the role ascribed to CCR1 and its chemokine ligands on osteoclast precursors and mature osteoclasts.12 ,16,,18 Bone densitometry measurements were not performed in this clinical trial. However, as bone antiresorptive treatment typically leads to increases in bone mineral density,19 ,20 chronic CCX354-C treatment would probably increase bone mineral density. This salutary effect of CCX354-C treatment might help protect bone in patients with RA. Further study in this regard is justified. iPTH levels were not significantly affected by CCX354-C treatment, indicating that CCX354-C did not induce secondary hyperparathyroidism.

Subjects with good CCX354 plasma exposure throughout the dosing period typically were ACR20 responders in both CCX354-C groups, indicating that a minimum plasma concentration of 100 ng/ml typically results in clinical efficacy. However, efficacy observed with 200 mg once daily generally appeared higher than with 100 mg twice daily, and as Cmax with 200 mg once daily was approximately 64% higher than with 100 mg twice daily, higher plasma coverage is probably desirable for optimal efficacy. As no dose-limiting toxicity has been observed with a daily dose of 200 mg, higher doses could be explored in future.

Other CCR1 antagonists have been studied in RA. Clinical trials have been reported previously with CP-481,715 in healthy volunteers or patients with RA,6 ,21 ,22 BX471 in multiple sclerosis,23 ,24 AZD4818 in chronic obstructive pulmonary disease25 and MLN3897 in RA.26 Clinical trials with CP-481,715 showed encouraging results: the drug reduced nickel-induced skin reactions in allergic subjects,21 it blocked macrophage inflammatory protein-1α-induced CD11b upregulation in monocytes,22 and it reduced the number of macrophages, intimal macrophages, and CCR1+ cells in the synovium of patients with RA in a phase Ib clinical trial.6 Projected CCR1 plasma coverage was very high with CP-481,715.13 Results from clinical trials with BX471,23 ,24 AZD481825 and MLN389726 were negative, possibly due to inadequate CCR1 blockade.13 Therefore, sufficient CCR1 blockade, as was achieved with CP-481,715 and now with CCX354-C, results in clinical and biological activity.13 ,27 Furthermore, as RA is a prototypic immune-mediated inflammatory disease, these findings may pave the way for future studies exploring CCR1 blockade in other conditions. Finally, results from in-vitro migration studies and clinical trials in RA targeting CCR2 or CCR5 have been negative, indicating that these may not be good chemokine receptor targets in RA.28,,30

Targeting the chemokine system offers the prospect of organ-specific immunotherapy not just for RA, but also a wide variety of immunologically mediated diseases.27 For example, the C-C chemokine receptor CCR9 specifically enables inflammatory cell infiltration into the intestinal mucosa in inflammatory bowel disease such as Crohn's disease. An orally administered specific CCR9 antagonist, CCX282-B, blocks this inflammatory cell infiltration and is currently in phase 3 development for Crohn's disease.31

This study includes only subjects on methotrexate. It is unknown whether CCX354-C would be effective in subjects who are naive to RA treatment or on biological treatment. Based on the finding that CCX354-C was well tolerated at a daily dose of 200 mg, it is anticipated that higher doses could be explored in future.

Limitations of this trial include the relatively small sample size and limited duration of dosing. Future larger and longer-term clinical trials are planned.

In conclusion, results from this clinical trial suggest that CCX354-C, an orally administered, specific CCR1 antagonist, provides a novel approach to modulate synovial inflammation, and may be an effective therapy for RA.

References

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Review history and Supplementary material

  • Supplementary Data

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Footnotes

  • Collaborators The CARAT-2 Study Group. The investigators who contributed to CCR1 Antagonist Rheumatoid Arthritis Trial 2 (CARAT-2) are listed in the supplementary appendix, which is provided online only.

  • Competing interests PPT became an employee of GlaxoSmithKline after study completion. GSK has a proprietary interest in CCX354-C by virtue of an alliance with ChemoCentryx the sponsor company. ChemoCentryx and GSK funded the study.

  • Ethics approval Each study centre obtained ethics committee approval for the trial before the enrolment of any study subjects.

  • Patient consent Obtained.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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