COMBO-IBD Study -Combination Immunomodulator Use and Thresholds

AJ Yarur et al. Clin Gastroenterol Hepatol 2023; 21: 2908-2917. Open Access! Combination Therapy With Immunomodulators Improves the Pharmacokinetics of Infliximab But Not Vedolizumab or Ustekinumab

In this prospective cohort with 369 patients, treatment included the following 113 infliximab, 133 vedolizumab, and 123 ustekinumab. All patients received standard dosing (eg. 5 mg/kg/dose every 8 weeks with infliximab). Per Table 1, dose of thiopurine was 100 mg (range 50-150, “using a 2:1 ratio of azathioprrine and mercaptopurine”); most patients received methotrexate at a dose of 12.5 mg. Key findings:

  • Infliximab levels were much improved in patients receiving combination therapy with either a thiopurine or methotrexate. In those patients receiving a thiopurine, a threshold of 6-TGN ≥146 was considered optimal.
  • Patients receiving combination therapy with methotrexate or a thiopurine and a 6-TGN concentration ≥146 pmol per 8 × 108 RBCs, and those with baseline infliximab level ≥12.3 μg/mL had a lower rate of secondary nonresponse when compared with those on monotherapy, thiopurine with 6-TGN <146 pmol per 8 × 108 RBCs, and baseline infliximab level <12.3 μg/mL (88.2 vs 11.8% [P = .04], 71.2 vs 45.5% [P = .04])
  • Ustekinumab and vedolizumab levels were NOT increased in patients receiving an immunomodulator

My take: This study reinforces the idea that there are pharmacokinetic benefits of combination therapy with infliximab (and extrapolated to other anti-TNF agents); there is a lack of benefit for most patients receiving ustekinumab and vedolizumab. Even with ustekinumab and vedolizumab, it is possible that patients with more severe disease may still benefit independent of pharmacokinetic effects on biologic agent.

Higher doses of infliximab monotherapy with therapeutic drug monitoring may achieve similar results as combination therapy. However, patients switching from one anti-TNF to another due to immunogenicity/antidrug antibodies are particularly likely to benefit from combination therapy. In addition, a recent ImproveCareNow study showed better outcomes for pediatric patients who received methotrexate with adalimumab (see below).

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