Purpose of this study is to assess the safety and tolerability of multiple ascending subcutaneous doses of REGN3500 to moderate asthmatics.

Key Inclusion Criteria:

• Body mass index (BMI) of 18 to 32 kg/m2
• A diagnosis of moderate asthma (according to GINA 2015) for a period of at least 2 years prior to screening.
• Patient must use a stable medium daily dose level of inhaled corticosteroids (ICS) as defined by GINA guidelines, ie, total daily dose of ICS >400 μg and ≤800 μg/day of budesonide or equivalent for at least 1 month prior to screening and during the study
• A pre-bronchodilator forced expiratory volume in the first sec (FEV1) ≥60% and ≤90% of the predicted normal values at screening and pre-dose at screening
• A documented positive response to the reversibility test at the screening, defined as improvement in FEV1 ≥12% and ≥200 mL over baseline after 400 μg salbutamol Pmdi
• Willing and able to comply with clinic visits and study-related procedures
• Provide signed informed consent.

Key Exclusion Criteria:

• Clinically significant abnormal CBC, clinical chemistry, and urine analysis at screening.
• Treatment with an investigational drug within 8 weeks or within 5 half-lives (if known), whichever is longer, prior to screening.
• History of life-threatening asthma
• Occurrence of asthma exacerbations or respiratory tract infections within 4 weeks prior to screening.
• Diagnosis of any other airway/pulmonary disease such as Chronic Obstructive Pulmonary Disease (COPD) as defined by the Global Initiative for Chronic Obstructive Lung Disease (GOLD) guidelines (GOLD 2016); or other lung diseases (eg, emphysema, idiopathic pulmonary fibrosis, Churg-Strauss syndrome, allergic bronchopulmonary aspergillosis cystic fibrosis, bronchiectasis or alpha-1 antitrypsin deficiency or restrictive lung disease).
• Chronic or acute infection requiring treatment with systemic antibiotics, antivirals, or antifungals within 1 month prior to screening.
• Use of oral antibiotics/anti-infectives within 2 weeks prior to screening.
• Known sensitivity to doxycycline or tetracyclines, or to any of the components of the investigational product formulation.
• Recent (within the previous 2 months) bacterial, protozoal, viral, or parasite infection.
• History of tuberculosis or systemic fungal diseases
• Patients treated with a monoclonal antibody based therapy (such as an anti-IgE, anti-IL-5), a biologic therapy or immunotherapy (subcutaneous immunotherapy [SCIT], sublingual immunotherapy [SLIT], or oral immunotherapy [OIT]) in the previous 12 weeks prior to screening and during the study

Note: Other protocol defined Inclusion/Exclusion criteria may apply