Retrospective Non-Interventional Assessment of the Use of Idelalisib in Relapsed/Refractory Chronic Lymphocytic Leukemia Patients in Spain

Background

Idelalisib is a PI3-kinase inhibitor specific for the delta isoform, approved (in combination with rituximab or ofatumumab) for the treatment of adult patients with Relapsed/Refractory Chronic Lymphocytic Leukemia (R/R CLL). Although the efficacy of idelalisib was reported in clinical trials, it is unclear how this translates into Real World.

Methods

A non-interventional retrospective study was conducted in Spain to describe the clinical characteristics and outcomes of patients diagnosed with R/R CLL that started treatment with idelalisib between 1 February 2015 and 31 December 2017.

The Time from start of idelalisib treatment to either the start of a new anti CLL therapy or death (Time to Next Treatment or Death - TNTD) was defined as primary endpoint. Secondary endpoints included overall survival (OS), time to discontinuation (TTD) and safety, especially Adverse Events of Special Interest (AESI):

• ≥ grade 3 transaminase elevations, diarrhea /colitis, pneumonitis, neutropenia,

• Cytomegalovirus, bacterial, fungal and respiratory virus infections (RVI),

• Pneumocystis jirovecii pneumonia (PjP).

Results

Investigators from 21 centers included 77 patients in the study. The median age was 72.1 years (48-86) and 67.5% (n=52) were male. The main baseline characteristics were: Binet stage B-C in 32.5% (n=25), 17p deletion or TP53 mutation in 35.1% (n=27) and the median number previous lines of therapy was 4 (1-16).

With a median follow up time of 14.4 months (1.2-44.4), 27 patients (35.1%) had started a new treatment and 19 (24.7%) had died.

The median TNTD was 17.1 months (95% CI 14.0-22.3) in the overall population and 13.8 months (95% CI 7.9-15.2) in patients that discontinued idelalisib.

The median OS has not been reached, with a cumulative probability of surviving at 1 and 2 years of 0.84 (95% CI 0.73-0.91) and 0.67 (95% CI 0.52-0.78).

During follow-up 54 patients (70.1%) discontinued idelalisib: 39 (72.3%) due to toxicity and 10 (18.5%) due to disease progression. The median TTD was 13.0 months (95% CI 7.7-15.8); 5.3 months (95%CI 3.8-8.0) in patients who discontinued treatment due to serious adverse events (SAE) or AESI and 10.5 months (95% CI 0.5-16.0) in those who did so due to progressive disease.

A total of 355 AEs were reported, of which 29.0% (n=103) were SAE.

181 AESIs were recorded: the most frequent were neutropenia (n=67; 22 grade >3), diarrhea/colitis (n=37; 14 grade >3) and bacterial infections (n=24; 14 grade >3). Other AESI were CMV infections (n=11), grade ≥ 3 pneumonitis (n=7), RVI (n=6), fungal infections (n=5), grade ≥ 3 transaminase elevations (n=3) and PjP (n=1). The median time from Idelalisib start to first AESI was 9.5 months (95%CI 5.5-15.3).

During follow-up, 19 deaths were registered, 10 of which were caused by idelalisib-related SAEs (4 respiratory infections, 2 pneumonitis, 1 diarrhea/colitis). The time from SAE related to idelalisib that led to death, to death was 0.8 months (95% CI 0.7-1.7).

Conclusions

This real world study shows results of effectiveness of idelalisib consistent with the efficacy findings of the 312-0116 clinical trial. Toxicity was the most common reason for idelalisib discontinuation. Findings of adverse events were consistent with the known safety profile of idelalisib and no new drug-related adverse events were identified.

This is a Gilead Sciences sponsored study.

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