This is a 12 weeks study aimed at assessing the safety and efficacy of 2 doses of AB1010 in patients suffering from indolent systemic mastocytosis with handicap.

Efficacy will be assessed based on:

Pruritus score Number of flush per day Pollakyuria (on a daily basis) Number of stools per day QLQ-C30 score Hamilton Rating Scale for depression

Inclusion Criteria:

1. Patients with documented Indolent systemic mastocytosis with handicap (ISMwh) having at least 2 infiltrated* organs (skin and /or bone-marrow and/or internal organ).

2. Bone-marrow, or skin or internal biopsy-documented mastocytosis and evaluable disease.

3. The absence of an activating point mutation in the phosphotransferase domain of c-Kit such as D816V c-Kit mutation in at least one of the two infiltrated organs: bone marrow and/or skin and/or other tissue.

4. Handicap defined as at least one of the following handicaps:

   • a number of flush per day ≥ 1 ,
   • a pruritus score ≥ 9 ,
   • a number of stools per day ≥ 4 ,
   • a Pollakyuria (on a per day basis) ≥ 8 ,
   • a QLQ-C30 score ≥ 83 ,
   • a Hamilton rating scale for depression ≥ 12

Exclusion Criteria:

1. Performance status > 2 (ECOG).
2. Inadequate organ function, except if the abnormalities are due to involvement by mast cells