Background: Mast cells help the body fight disease and heal wounds. People with indolent systemic mastocytosis (ISM) make too many mast cells. This causes pain, tiredness, digestive problems, and other symptoms. Researchers think the drug sarilumab could help. Objective: To see if sarilumab is a safe and effective treatment for people with ISM. Eligibility: Adults ages 18-75 with ISM who are enrolled in NIH study 02-I-0277 Design: Participants will be screened with: - Physical exam - Medical history - Blood and urine tests - Questionnaires - Bone marrow removed by a needle inserted into the hip bone - Ultrasound of the abdomen - Photographs of the skin Participants will repeat some screening tests at study visits. Participants will have a baseline visit in the hospital for 3 days. They will: - Be assigned to get either the study drug or a placebo. They will not know which one they get. - Have a skin punch biopsy: An instrument will remove a small piece of skin. - Get their first drug dose injected under their skin Participants will keep a side effect and medication diary during the study. Participants will visit the clinic to get a drug dose every 2 weeks, for a total of 8 doses. Participants will have a visit 2 weeks after their final dose. It will last up to 2 days. Participants will have another visit 12 weeks later. Participants may then continue this study for 1 more year. Those who continue will get sarilumab, even if they previously got the placebo, every 2 weeks. They will have visits every 6 weeks, and then every 3 months.
Name: Sarilumab
Name: Placebo
Description: frequency and severity of adverse events during the randomized double-blinded placebo-controlled treatment period
Measure: Frequency and severity of adverse events (AEs) Time: day 0 through week 28Description: QoL at 16 weeks post-initiation of study drug/placebo using the Mastocytosis Quality of Life Questionnaire (MC-QoL).
Measure: Mastocytosis Quality of Life Questionnaire (MC-QoL). Time: 16 weeks post study drug initiationDescription: Reduction of percentage infiltrating mast cells in bone marrow. Decrease in the allelic frequency of D816V using PCR
Measure: mast cells in bone marrow and allelic frequency of D816V Time: Day 0 and Week 16 for bone marrow and Day 0, week 16 and week 28 for D816V allelic FrequencyDescription: Percent improvement in QoL using MC-QoL, scoring of mastocytosis index (SCORMA), and Memorial Symptom Assessment Scale (MSAS) and the Mastocytosis Quality of Life Questionnaire (MQLQ), and the mastocytosis Symptom Assessment Form (MSAF)
Measure: Questionnaires MC-Qol, MSAS, SCORMA, MQLQ, MSAF Time: Day 0 through Week 28Description: Reduction in use of medicines for symptomatic relief, reduction in serum levels of tryptase
Measure: Reduction in use of medicines and reduction in serum Tryptase Time: Day 0 through Week 28Allocation: Randomized
Parallel Assignment
There is one SNP
Mastocytosis Quality of Life Questionnaire (MC-QoL).. QoL at 16 weeks post-initiation of study drug/placebo using the Mastocytosis Quality of Life Questionnaire (MC-QoL).. mast cells in bone marrow and allelic frequency of D816V. --- D816V ---
Decrease in the allelic frequency of D816V using PCR. --- D816V ---