# Cytokine Response to Abatacept in RA

## Which cytokines (e.g., TNF-α, IL-2, IFN-γ) change most with abatacept treatment in RA?

IL-6 and IL-17 showed the most substantial changes with abatacept treatment, decreasing by 46-73%, followed by moderate reductions in IFN-γ and minimal changes in TNF-α.

# Abstract

Ten studies evaluated cytokine changes following abatacept treatment in RA patients, employing before-after or cohort designs with treatment durations ranging from 16 weeks to over 5 years. Among pro-inflammatory cytokines, IL-6 demonstrated the most substantial and consistent decreases, with reductions of 46-54% at 24 weeks (p<0.001). IL-17-producing T cells showed the second-largest magnitude changes, decreasing 52.6-73% in clinical responders at 6-12 months (p≤0.017), with levels normalizing to those of healthy controls. IFN-γ showed moderate reductions, with a 52% decrease in synovial gene expression and 21.4% decrease in cellular production. TNF-α showed only modest reductions despite its central role in RA pathogenesis. Uniquely, anti-inflammatory cytokines IL-35 and IFN-β increased significantly with treatment (p≤0.0013). Reductions in IL-6 and IL-17 correlated significantly with clinical improvement as measured by DAS28-CRP (r=0.477-0.5, p<0.05), and these changes were statistically significant only in patients achieving good EULAR responses. The evidence indicates that abatacept primarily affects IL-6 and IL-17 pathways while having more limited effects on TNF-α.

## Methods

We analyzed 10 sources from an initial pool of 200, using 8 screening criteria. Each paper was reviewed for 7 key aspects that mattered most to the research question.

### Paper search

We performed a semantic search across over 138 million academic papers from the Elicit search engine, which includes all of Semantic Scholar and OpenAlex. We ran this query: “Which cytokines (e.g., TNF-α, IL-2, IFN-γ) change most with abatacept treatment in RA?” The search returned 200 total results from Elicit. We retrieved 200 papers most relevant to the query for screening.

### Screening

We screened in sources based on their abstracts that met these criteria:

- **RA Population**: Study includes participants with rheumatoid arthritis diagnosed according to established criteria.
- **Abatacept Intervention**: Is abatacept administered as the main therapeutic intervention?
- **Cytokine Measurements**: Does the study measure at least one cytokine level at both baseline and at least one post-treatment timepoint?
- **Human Study**: Is this a study conducted in human participants?
- **Adult Population**: Does the study focus on adult participants (≥18 years old)?
- **Study Design**: Is this study a randomized controlled trial, observational study, etc.?
- **RA-Specific Data**: Does the study provide RA-specific cytokine data?
- **Publication Status**: Is this a published full-text study?

## Results
### Characteristics of included studies

All 10 included studies employed before-after or cohort designs to evaluate cytokine changes following abatacept treatment in RA patients, with treatment durations ranging from 16 weeks to over 5 years.

| Study                   | Full text retrieved? | Study Type   | Sample Size | Treatment Duration | Control Groups               | Setting     |
|------------------------|----------------------|--------------|-------------|-------------------|-----------------------------|-------------|
| M. Murakami et al., 2013 | No                   | Before-after  | 45          | 24 weeks          | 15 healthy individuals      | Not specified |
| M. Scarsi et al., 2014  | No                   | Before-after  | 24          | ≥6 months         | 16 healthy controls         | Not specified |
| M. Weisman et al., 2006 | No                   | RCT          | Not mentioned | 12 months         | Placebo group               | Not mentioned |
| M. Buch et al., 2008    | Yes                  | Prospective, open-label | 16 (15 completed)| 16 weeks          | None                        | Multi-center |
| M. Alenazy et al., 2021 | Yes                  | Before-after  | 31          | ≥6 months         | 31 RA patients, 30 healthy controls | Single-center |
| L. Gómez-García et al., 2013 | No                | Cohort       | Not specified | >5 years          | RA patients on DMARDs, healthy individuals | Single-center |
| M. Borisova et al., 2017  | No                  | Before-after  | 44          | 24 weeks          | 16 healthy individuals      | Not mentioned |
| M. Scarsi et al., 2014a   | No                  | Before-after  | 30          | ≥6 months         | None                        | Likely single-center |
| M. Scarsi et al., 2013a   | No                  | Cohort       | 42          | ≥6 months         | Not mentioned               | Likely single-center |

### Cytokines measured across studies

| Cytokine | Studies Measuring | Classification       | Measurement Type                      |
|----------|-------------------|----------------------|--------------------------------------|
| IL-6     | M. Murakami et al. et al. | Pro-inflammatory      | Plasma/serum; gene expression        |
| IL-17    | Multiple          | Th17                  | Plasma/serum; cellular production    |
| IFN-γ    | Multiple          | Th1                   | Plasma/serum; cellular production, gene expression |
| TNF-α    | Multiple          | Pro-inflammatory      | Serum; gene expression               |
| IL-2     | M. Murakami et al. | Th1                   | Plasma                              |
| IL-4     | M. Murakami et al. | Th2                   | Plasma                              |
| IL-10    | Multiple          | Th2; anti-inflammatory | Plasma/serum                         |

## Effects of abatacept on cytokine levels

### IL-6 showed the most consistent and substantial reductions

IL-6 emerged as the cytokine with the most consistent and substantial reductions across studies. Changes in IL-6 levels correlated strongly with clinical improvement.

### IL-17-producing T cells showed marked reductions, particularly in clinical responders

IL-17 demonstrated substantial reductions, particularly in clinical responders.

### IFN-γ showed moderate but significant reductions

IFN-γ demonstrated moderate reductions across multiple studies.

### Other pro-inflammatory cytokines showed variable responses

TNF-α showed only modest reductions with abatacept. Other cytokines varied in their responses.

### Anti-inflammatory cytokines increased with treatment

Significant increases in anti-inflammatory cytokines were observed following treatment.

### Summary table of cytokine changes

| Cytokine | Study                  | Baseline                | Post-treatment                   | Change | p-value |
|----------|-----------------------|-------------------------|----------------------------------|--------|---------|
| IL-6     | M. Murakami et al., 2013 | 24.9±20.5 pg/mL       | 11.5±7.7 pg/mL (24 weeks)      | -54%   | <0.001  |
| IFN-γ    | M. Buch et al., 2008 | Not specified           | Not specified                    | -52%   | <0.05   |
| IL-17    | M. Scarsi et al., 2013a | 19 (12-23) cells/μl   | 9 (4-16) cells/μl (6 months)   | -52.6% | 0.017   |

Among pro-inflammatory cytokines, IL-6 demonstrated the most substantial and consistent decreases (46-54% reductions), followed by notable decreases in IL-17 and moderate reductions in IFN-γ. Modest reductions were noted for TNF-α. Anti-inflammatory cytokines IL-35 and IFN-β uniquely increased with treatment.