Evaluation of the Impact of the Presence of Neutralizing L-Asparaginase Antibodies on the Efficacy and Safety of Graspa in Phase 3 Randomized Trial Versus Native L-Asparaginase in Patients with Relapsed Acute Lymphoblastic Leukemia (NCT01518517)

Background

Asparaginase is a cornerstone in the treatment of ALL, but its utility is limited by toxicities including hypersensitivity. Clinical allergy is associated with inactivation of asparaginase by antibodies, which can also neutralize asparaginase without any clinical signs of hypersensitivity (silent inactivation). GRASPA (eryaspase - proposed INN) is an L-asparaginase encapsulated into the red blood cells. In a recent Phase III trial, it has shown to prolong the asparaginase activity and significantly reduce the incidence of allergic reactions in pts with relapsed ALL.

Methods

This open, randomized international Phase 3 study enrolled pts with relapsed ALL. The co-primary endpoints were the mean duration of asparaginase (ASPA) activity > 100 IU/L and incidence of hypersensitivity reactions during induction phase. Key secondary endpoints were safety, tolerability, complete remission and minimal residual disease rate, PK, and anti-ASPA antibodies (A-Abs) at baseline. Pts (n=80), aged 1-55 years without prior hypersensitivity were randomized to GRASPA (150 IU/kg, n=26, Arm A) or native L-asparaginase (L-ASP, 10,000 IU/m², n= 28, Arm B). Additionally, 26 pts with prior hypersensitivity were treated with GRASPA in a single stratum (Arm C). All pts received COOPRALL protocol as a backbone chemotherapy. Here we report the impact of A-Abs on safety and efficacy of GRASPA. Assessments were performed at Day 4, 13, 18, and 27 (F1/F2 block), Day 6, 15, and 27 (VANDA block), and Day 6, 12 (R2/R1 block).

Results

At baseline, 23%, 25%, and 58% of pts had +ve A-Abs status in Arms A, B, and C, respectively. The mean duration of total ASPA activity (Days) adjusted for baseline antibody status is presented below, and shows that activity slightly differed with positive status; however, GRASPA maintained higher activity compared to L-ASP:

 

	GRASPA	L-ASP	GRASPA	L-ASP	GRASPA (Arm C)
Antibody status	Negative		Positive		Negative	Positive
N	20	21	6	7	11	15
Mean (SD)	22.4  (3.6)	10.31  (8.1)	14.17  (5.1)	6.5  (4.0)	18.9  (6.8)	18.4  (6.2)
Median	22.4	8.3	12.2	7.0	21.8	21.7
Min; Max	10.2; 30.7	0.0; 25.0	9.8; 21.8	1.9; 14.0	9.1; 27.9	6.9; 25.0

The incidence of hypersensitivity reactions were 0%, 7/21 (33%), and 2/11 (18%) in pts with negative A-Abs, compared to 0%, 6/7 (85.7%), and 1/15 (7%) in pts with positive A-Abs, in arms A, B and C, respectively.

The CR rate during induction was 75%, 48%, and 64% in pts with negative A-Abs, compared to 33%, 14% and 48% in pts with positive A-Abs, in arms A, B and C, respectively.

Conclusion

These results show that about one third of pts without evidence of prior hypersensitivity have silent A-Abs activation. Positive A-Abs appeared to attenuate the clinical activity in all treatments arms. GRASPA consistently demonstrated activity and improved hypersensitivity regardless of A-Abs status, and therefore, GRASPA is a suitable option for patients with relapsed ALL.