BCR-Assosiated Kinase Inhibition in Relapsed/Refractory Chronic Lymphocytic Leukemia. Real World Experiences of a German Regional Clinical Register

Background:

The advent of B-cell-receptor associated kinase inhibition (BCR-KI) inaugurated a novel therapeutic principle in chronic lymphocytic leukemia (CLL). First-in-class Ibrutinib (Ib) and Idelalisib (Id) received marketing authorization from the EMA for the treatment of relapsed/refractory (r/r) CLL in 2012 and 2014, respectively. In spite of ample evidence from trials, real life data are scarce.

Methods:

Our clinical registry has been previously described in detail [https://doi.org/10.1182/blood-2018-99-110618]. It comprises of 168 unselected CLL patients (pts.), who were observed between 10/2014 and 08/2020. 65 of them required treatment during this period: 39 x 1st line only and 26 x > 2nd line. 18 of these 26 r/r CLL pts were treated either with Ib (11 x) or Id (7 x). Treatment was started according to iwCLL guidelines. The type of BCR-KI was chosen based on an individual's performance status, previous treatment and co-morbidity.

Median 1^st line-treatment (as a rule immunochemotherapy) started 27.5 months (m) after diagnosis (range: 0.5 m to 87.5 m). Time from 1^st line therapy to BCR-KI treatment ('Ctx effected time') was 13.0 to 128.1 m (median 50.5 m), in total (18 pts.) 1052.5 m, i.e. 87.7 years (y). 17 of 18 pts. had received Rituximab (R) as part of a pre-BCR-treatment protocol.

Estimated charges per month are 9.000 € in Id + R, 7.000 € in R + chemotherapy (ctx, i.e. Fludara or Bendamustin mostly) and 4.500 € in Ib or Id mono or R + Chlorambucil (Clb) respectively.

Results:

Patients described herein differed according to age at start of BCR-KI (44.4 to 86.8 y, median 76.0 y), sex (10 m, 8 f), types and lines (1 to 6, median 2) of prior treatment.

Indications for BCR-KI were increasing tumor burden (17 x, 1 x combined with pleural effusion) and persistent hemolysis (1 x). Genetic high risk features comprised of at least one of the following: IGHV unmutated status, mutation and/or deletion of TP53 gene, deletion of 11q, and complexe karyotype. These features were present in 17 of 18 pts. (median 3 features). In particular, unmutated IGHV was found in 13/18 r/r pts who received BCR-KI (total cohort of r/r pts, 21/26).

Overall response rate was 78% (Ib 8/11; Id 6/7). Time to next therapy or death (`KI effected time`) varies from 1.1 m to 69.1 m - in total 286.9 m until now. 4 pts. continued BCR-KI from 30 to 67 months. This was always the longest period of unchanged therapy in these 4 pts. Shorter `KI effected time` in the other 14 pts. was associated with higher treatment line and treatment interruptions. 2 responding pts. (without side effects) stopped BCR-KI and stayed in ongoing hematological remission for 11 and 25 months after cessation of treatment.

Adverse drug reactions occurred in 6 pts. (Ib 4 x, Id 2 x). 5 pts. died on BCR-KI, but there was no therapy related death. Approximate costs per month in Germany are 1700 € in `Ctx effected time` (1.800.000 € per 1052,9 m) and 4.700 € in `KI effected time` (1.350.000 € per 286,9 m).

Of note, one pt. on Id showed clinical progression associated with genetic evolution after 67 months of BCR-KI. He promptly responded to venetoclax.

Discussion:

In real live many r/r CLL pts. are elderly and present a broad spectrum of different clinical features. A clinical registry can reflect this and may add to our knowledge from multicenter studies. Remarkably almost all of our unselected r/r CLL pts. revealed genetic high risk features, in particular unmutated IGHV status, making them ideal candidates for targeted treatment strategies. These strategies take advantage of the fact that BCR-KI has been demonstrated to be well tolerated and effective in elderly and pre-treated pts.

Undoubtedly BCR-KI increases the total costs of therapy, but affords a prolongation of overall survival. Remaining open questions include optimal treatment sequences, combination partners for BCR-KI as well as thorough analysis in the quality of molecular remissions.