Approach can reduce drug-induced TLS

All patients should receive oral hydration prior to receiving ABT-199, and hospitalized patients should receive intravenous hydration (150-200 cc/hour, as tolerated).

All patients should receive a uric-acid-reducing agent at least 72 hours before their first dose of ABT-199. Rasburicase is strongly suggested for high-risk patients with high baseline uric acid and for patients who develop rapid rises in uric acid values.

The researchers also recommended laboratory assessment at 8 hours and 24 hours in an outpatient setting and at 4, 8, 12, and 24 hours in hospitalized patients.

Approach reduces TLS risk

Lastly, Dr Seymour and his colleagues analyzed the effect of the modified dosing schedule and the aforementioned prophylactic measures on a cohort of 58 CLL/SLL patients treated with ABT-199.

The TLS risk stratification was similar in this cohort and the pre-modification cohort of 77 patients. There was, however, a higher proportion of patients in the post-modification cohort who fell into the high-risk category.

According to Cairo-Bishop criteria, 3 patients (3.9%) had clinical TLS in the pre-modification cohort and 16 (20.8%) had laboratory TLS. In the post-modification cohort, none of the patients had clinical TLS, and 8 (13.8%) had laboratory TLS.

According to the Howard definition of TLS, 3 patients (3.9%) in the pre-modification cohort had clinical TLS, and 7 (9.1%) had laboratory TLS. But none of the patients in the post-modification cohort had clinical or laboratory TLS.

Phase 1 trial of ABT-199 monotherapy

In another presentation at the EHA Congress, Dr Seymour reported results from a phase 1 study of ABT-199 monotherapy in 105 patients with high-risk CLL/SLL.

Following the identification of TLS, patients received treatment according to the modified schedule, as well as TLS prophylaxis.

In all, 7 patients developed TLS. One of these patients died, and 1 required dialysis. As of April 9, 2014, there were no cases of TLS among the 49 patients who received ABT-199 according to the modified dosing schedule, as well as TLS prophylaxis.

Other common treatment-emergent adverse events included diarrhea (40%), neutropenia (36%), and nausea (35%). Grade 3/4 neutropenia occurred in 33% of patients, and febrile neutropenia occurred in 4%.

Thirty-seven patients discontinued treatment—22 due to progressive disease, 12 due to adverse events, and 3 for other reasons (1 required warfarin, and 2 proceeded to transplant).

Seventy-eight patients were evaluable for treatment response. Nineteen of these patients had del (17p), 41 were fludarabine-refractory, and 24 had unmutated IGHV.

The response rate was 77% overall, 79% among patients with del (17p), 76% in those who were fludarabine-refractory, and 75% in those with unmutated IGHV. The complete response rates were 23% 26%, 22%, and 29%, respectively.

As of April 9, the median progression-free survival was about 18 months. The median progression-free survival had not been reached for patients treated at or above 400 mg.