Upadacitinib

The Janus kinases (JAKs) are a family of cytoplasmic tyrosine kinases whose function is to transduce cytokine-mediated signals via the JAK-STAT pathway. There are four JAK subtypes, each of which has overlapping receptor responsibilities. Inhibitors of this enzyme family (jakinibs) have shown efficacy in treating certain inflammatory and autoimmune diseases such as rheumatoid arthritis and Crohn's disease. However, the first generation of these drugs, tofacitinib and ruxolitinib, lacked subtype selectivity, affecting JAK1/JAK3 and JAK1/JAK2 respectively. This has led to dose-limiting side effects in this otherwise promising class of drugs.[10][11] Upadacitinib is a second generation Janus kinase inhibitor that is selective for the JAK1 subtype of this enzyme over the JAK2 (74-fold), JAK3 (58-fold) and tyrosine kinase 2 subtypes.[12]

After oral intake, upadacitinib reaches highest concentrations in the blood plasma after two to four hours. A fatty meal has no clinically relevant effect on its resorption. Steady-state conditions are reached after four days; accumulation is minimal. There is no significant first pass effect. When in the bloodstream, 52% of the substance are bound to plasma proteins. It is mainly metabolized by CYP3A4, and possibly to a minor extent by CYP2D6. The most important pathway consists of oxidation to a carboxylic acid and subsequent glucuronidation, yielding a metabolite called M4. However, 79% of the drug are circulating in form of upadacitinib itself, and only 13% as M4. Other metabolites are only present in small fractions. None are pharmacologically active.[6][9]

The drug is excreted mainly as the original substance, of which 38% are found in the feces and 24% in the urine. The mean terminal half-life is 9 to 14 hours.[6][9]

A phase I study revealed that upadacitinib followed a bi-exponential disposition with a terminal half-life of 6–16 hours.[5] There was no significant accumulation over the dose range of 3–36 mg per day. No interaction was found in rheumatoid arthritis patients taking methotrexate. The most common adverse event was headache but its incidence was similar to that when taking placebo (15.6% for upadacitinib vs. 16.7% for placebo). An investigation into absorption and metabolism found that dosing after a high-fat meal had no effect on upadacitinib total drug exposure over time (area under the curve or AUC).[13] Inhibition of CYP3A by ketoconazole increased total AUC, indicating the importance of this metabolic route.

Two phase IIb studies were initiated to study the efficacy and safety of upadacitinib in patients with rheumatoid arthritis and one phase II study was initiated in patients with Crohn's disease.

In the first study, 276 rheumatoid arthritis patients were recruited who had previously experienced inadequate response to anti–tumor necrosis factor (TNF) therapy and were currently on a stable dose of methotrexate.[14] Patients were randomized to receive 3, 6, 12, or 18 mg twice daily or placebo. The primary endpoint was a 20% improvement in symptoms according to the American College of Rheumatology improvement criteria (ACR20). At the completion of the study it was found that response rates were significantly higher in those receiving upadacitinib versus in those receiving placebo alone (36–42% and 22– 26%, respectively). Adverse events included headache, nausea, and infection but no infections were serious.

In the second phase IIb study, 300 rheumatoid arthritis patients were recruited who have had an inadequate response to methotrexate.[15] Patients were randomized to receive 3, 6, 12, or 18 mg twice daily or placebo. The primary endpoint was a 20% improvement in symptoms according to the American College of Rheumatology improvement criteria (ACR20). At the completion of the study it was found that response rates were significantly higher in those receiving upadacitinib versus in those receiving placebo alone. (62%, 68%, 80%, 64%, and 76% for the 3, 6, 12, 18, and 24 mg doses, respectively) than with placebo (46%). Improvement in symptoms was rapid, with significant changes in disease scores by week 2. Adverse events were mild with infection being the most serious. One case of community-acquired pneumonia occurred at 12 mg.

In this 16-week study, 220 patients were recruited with moderately to severely active Crohn's disease. Participants must have also experienced an inadequate response to or intolerance to Immunotherapy or TNF inhibitors.[16][17] Patients were randomized to therapy with upadacitinib at 3, 6, 12, 24 mg twice daily or 24 mg once daily for 16 weeks or placebo, followed by blinded extension therapy for 36 weeks. The co-primary endpoints were the proportion of patients who achieved clinical remission (soft stool frequency or daily abdominal pain score) at week 16 and endoscopic remission at week 12 or 16. Secondary endpoints included significant clinical response (≥30% reduction in symptoms) at week 16 and endoscopic response (≥25% decrease in symptoms) at week 12 or 16. At 16 weeks 22% of patients taking the 24 mg twice daily dose achieved endoscopic remission with upadacitinib compared to 0% of patients taking placebo. 27% of patients taking the 6 mg twice daily dose achieved clinical remission compared to 11% of patients taking placebo. Adverse events did not appear to be dose-related. A single case of non-melanoma skin cancer was reported in the 24 mg twice daily group.

Abbvie has planned a total of six phase III trials that will evaluate over 4,000 patients with moderate to severe rheumatoid arthritis.[18] Two Phase III trials are planned studying participants with psoriatic arthritis and one in participants with ulcerative colitis.

In SELECT-COMPARE 1629 patients with moderate to severe rheumatoid arthritis and inadequate response to methotrexate were randomized (2:2:1) to once-daily upadacitinib 15mg, placebo, or adalimumab 40mg, on stable background methotrexate. Primary endpoints were ACR20 and DAS28CRP<2.6 versus placebo at week 12; inhibition of radiographic progression was evaluated at week 26. The study was designed and powered to test for non-inferiority and superiority of upadacitinib versus adalimumab clinically and functionally. At week 12, both primary endpoints were met for upadacitinib versus placebo (p≤0.001). ACR20 was achieved by 71% versus 36%, and DAS28CRP<2.6 by 29% versus 6%. Upadacitinib was superior to adalimumab for ACR50, DAS28CRP≤3.2, ΔPain and ΔHAQDI. At week 26, more patients on upadacitinib vs placebo or adalimumab achieved low disease activity or remission (p≤0.001). Radiographic progression was less and observed in fewer patients receiving upadacitinib versus placebo (p≤0.001). Up to week 26, adverse events (AEs) including serious infections were comparable for upadacitinib and adalimumab. The proportions of patients with serious AEs and AEs leading to discontinuation were highest for adalimumab; the proportion with herpes zoster and CPK elevations was highest for upadacitinib. Three malignancies, five MACE, and four deaths were reported, none on upadacitinib. Six venous thromboembolic events were reported [placebo, one; upadacitinib, two; adalimumab, three]. Upadacitinib was superior to placebo and adalimumab for improving signs, symptoms and physical function in RA patients on background methotrexate, and significantly inhibited radiographic progression versus placebo, while the overall safety profile was generally similar to adalimumab, except for higher rates of herpes zoster and CPK elevations on upadacitinib.[19]

SELECT-CHOICE was a phase III trial comparing upadacitinib and abatacept in 612 people whose rheumatoid arthritis did not respond to biologic DMARDs. It compared their ability to reduce Disease Activity Score-28 with CRP (DAS-28 CRP), a measure of rheumatoid arthritis disease severity that includes number of tender and swollen joints, C-reactive protein level (a marker of inflammation), and overall health reported on a standardized scale. The trial found that after 12 weeks of treatment, people treated with upadacitinib had lower DAS-28 CRP scores and a higher rate of remission. There was also a higher rate of serious and opportunistic infections, elevated liver enzymes, and thromboembolism in the upadacitinib group.[20][21]