Side effects that occurred early in people with multiple sclerosis during the first year of treatment with cladribine tablets: a plain language summary

People with multiple sclerosis (also shortened to MS) may have difficulties staying on treatment due to side effects. Cladribine tablets, approved for treating relapsing forms of MS, are given by mouth for four short periods over two years. The benefit of convenient dosing may be lost if side effects prevent people with MS from finishing their treatment. This is the summary of a study that examined side effects from cladribine tablets treatment in the first 12 weeks of two clinical studies called CLARITY and ORACLE-MS. Overall, 34.7% of participants who took cladribine tablets experienced drug-related side effects compared to 23.2% of participants who took placebo. Most side effects were mild and were seen in 54.8% of participants taking cladribine tablets and 59.1% taking the placebo. A low number of participants discontinued treatment due to side effects (1.6% of participants who took cladribine tablets; 1.4% of participants who took placebo). The researchers concluded that cladribine tablets are well-tolerated and people with MS are likely to complete the full treatment course. ClinicalTrials.gov NCT numbers: CLARITY study - NCT00213135 and ORACLE-MS study - NCT00725985.

Treatment-emergent adverse events occurring early in the treatment course of cladribine tablets in two phase 3 trials in multiple sclerosis

Background

Treatment-emergent adverse events (TEAEs) that occur close to treatment initiation may negatively affect overall tolerability and adherence. It is important to develop a clear understanding of potential early TEAEs after initiating treatment with cladribine tablets.

Objective

To identify TEAEs that begin early in the course of treatment in patients enrolled in CLARITY and ORACLE-MS studies.

Methods

This post hoc analysis of CLARITY and ORACLE-MS safety populations assessed the incidence of TEAEs, serious TEAEs, drug-related TEAEs, and TEAEs leading to discontinuation in patients receiving cladribine tablets or placebo within 2, 6, and 12 weeks after treatment initiation.

Results

By Week 12, 61.3% of patients treated with cladribine tablets 3.5 mg/kg and 55.2% treated with placebo experienced a TEAE. More patients receiving cladribine tablets versus placebo experienced a drug-related TEAE by Week 12 (34.7% vs. 23.2%). The most common TEAEs reported with cladribine tablets were: headache (7.2%), lymphopenia (6.8%), and nausea (6.0%). Patients receiving cladribine tablets and placebo reported similar proportions of serious TEAEs (2.2% vs. 1.7%) and TEAEs leading to treatment discontinuation (1.6% vs. 1.4%).

Conclusion

Cladribine tablets were well tolerated during the first 12 weeks as evidenced by a low incidence of TEAEs leading to treatment discontinuation.

Early MRI outcomes in participants with a first clinical demyelinating event at risk of multiple sclerosis in the ORACLE-MS study

Background

In the Phase 3, 96-week ORACLE-MS study, cladribine tablets 10 mg (3.5 or 5.25 mg/kg cumulative dosage over two years) significantly reduced lesions associated with multiple sclerosis versus placebo in participants following a first clinical demyelinating event (FCDE).

Objective

To determine the timing of effects of cladribine tablets on lesion activity assessed by magnetic resonance imaging (MRI).

Methods

This post hoc analysis assessed the effect of cladribine tablets versus placebo in ORACLE-MS on secondary MRI endpoints including T1 gadolinium-enhancing (Gd+), new or enlarging T2 lesions, and combined unique active lesions assessed on MRI scans performed at screening and every 3 months thereafter.

Results

Compared to placebo, cladribine tablets 3.5 mg/kg treatment appeared to lead to a trend of reductions in the mean number of T1 Gd+ lesions by Week 13 (first post-baseline scan: 0.37 vs. 1.00), new or enlarging T2 (0.20 vs. 1.01) and combined unique active (0.29 vs. 1.91) lesions by Week 24. Low lesion counts were maintained with cladribine tablets throughout 96 weeks. Similar results were observed with the 5.25 mg/kg dosage.

Conclusion

In participants with an FCDE, cladribine tablets appeared to reduce lesion numbers within 13 weeks (time of first evaluation).

Effects of cladribine tablets on lymphocyte subsets in patients with multiple sclerosis: an extended analysis of surface markers

Background

Cladribine tablets 3.5 mg/kg cumulative over 2 years (CT3.5) had significant clinical/imaging effects in patients with clinically isolated syndrome (CIS; ORACLE-MS) or relapsing-remitting MS (RRMS; CLARITY and CLARITY Extension). This analysis compared the effect of cladribine tablets on the dynamics of immune cell reduction and reconstitution in ORACLE-MS, CLARITY, and CLARITY Extension during the first year of treatment (i.e. the first course of CT1.75) in patients randomized to CT3.5.

Methods

Lymphocyte subtypes were analyzed using multiparameter flow cytometry. Changes in cell counts and relative proportions of lymphocytes were evaluated at weeks 5, 13, 24, and 48.

Results

Across studies, consistent and comparable selective kinetics of immune cell populations occurred following the first treatment year with CT. A rapid reduction in CD16⁺/CD56⁺ cells (week 5 nadir), a more marked reduction in CD19⁺ B cells (week 13 nadir), and a less-pronounced effect on CD4⁺ (week 13 nadir) and CD8⁺ T cells (week 24 nadir) was shown. There was little effect on neutrophils or monocytes. Lymphocyte recovery began after treatment with CT3.5. Regarding relative proportions of naïve and memory T-cell subtypes in ORACLE-MS, the proportion of naïve-like naturally occurring T-regulatory cells (nTregs) decreased, and the proportion of memory-like nTregs increased, relative to total CD4⁺ T cells.

Conclusions

CT3.5 has comparable effects on the immune systems of patients with CIS or RRMS. The pronounced reduction and recovery dynamics of CD19⁺ B cells and relative changes in the proportion of some immune cell subtypes may underlie the clinical effects of CT3.5.