• Male or females 18-75 years old.

• Subjects diagnosed with moderate-to-severe allergic asthma \[Global Initiative for Asthma \[GINA\]; GINA, 2021) at least 12 months prior to Visit 1.

• Documented reversibility from historical data of at least 12% and 200 mL in FEV1 after the administration of 200 to 400 mcg albuterol/salbutamol (or other standard office practice) OR documented airway hyperresponsiveness (methacholine PC20 \< 8 mg/mL \[or PC20 \< 16 mg/mL on ICS\]) OR airflow variability in clinic FEV1 \>12% and 200 mL between visits outside of respiratory infections, documented in the past 24 months prior to Visit 1 if documented reversibility and airway hyperresponsiveness data are not available.

• Subjects must have a pre-bronchodilator FEV1 value of ≥ 40% and ≤ 80% predicted within 2 months from randomization.

• Subjects must have received a physician-prescribed asthma regimen with medium- or high-dose ICS plus LABA for at least 3 month prior to Visit 1 and the dose of ICS must be stable for at least 30 days prior to Visit 1 and throughout the screening period.

∙ High-dose ICS is defined as total daily dose of \>500 mcg fluticasone propionate or equivalent

‣ Medium-dose ICS is defined as a total daily dose of 250 to 500 mcg fluticasone propionate or equivalent.

‣ Equivalence ICS doses will be based upon the GINA guidelines (GINA, 2021)

‣ According to the medical history, subject have no more than a maximum of 2000 mcg/day equipotent ICS daily dosage of fluticasone propionate or equivalent in 3 months before visit 1.

• Prior to screening, subjects must be on a stable dose of any of the following doses and formulations of ICS/LABA combination therapy for at least 1 month:

∙ Fluticasone/salmeterol combination therapy

⁃ Advair® Diskus - dry powder inhaler (DPI): 250/50 μg BID or 500/50 μg BID, or

• Advair® HFA - metered dose inhaler (MDI): 230/42 μg BID or 460/42 μg BID, or

‣ Budesonide/formoterol combination therapy (Symbicort® -160/4.5 μg BID or 320/9 μg BID), or

‣ Mometasone/formoterol combination therapy (Dulera® -200/10 μg BID or 400/10 μg BID).

‣ Other equivalents medium to-high dose medication following the GINA guidelines (GINA, 2021)

• Subjects must have a documented history of protocol-defined asthma exacerbation at least 1 or more times within the 12 months.

• A total serum IgE ≥ 125 IU/mL during screening prior to randomization.

• Subjects must have at least one positive in skin prick test or at least one environmental allergen-specific IgE greater than normal range.

⁃ Uncontrolled asthma demonstrated both during the screening period and at the time of randomization defined as ACQ-5 (5-item Asthma Control Questionnaire) ≥ 1.5

⁃ If recently treated for respiratory tract infection, the treatment must have been completed at least 4 weeks prior to screening. Subjects who have an upper respiratory tract infection during screening are allowed to be rescreened 4 weeks after resolution.

⁃ Female subjects of childbearing potential must use at least two forms of birth control. One must be barrier protection (i.e., condom or female condom) and the other is one of acceptable method of birth control (ie, diaphragm, intrauterine device, hormonal contraceptives, or abstinence) throughout the study. Subjects who are surgically sterile (ie, hysterectomy, bilateral tubal ligation, or bilateral oophorectomy), or postmenopausal (defined as amenorrhea for 12 consecutive months and documented serum follicle stimulating hormone level \>40 mU/mL) will be considered as no childbearing potential. All female subjects of child-bearing potential must have a negative serum pregnancy test at screening.

⁃ Note: The subject must use the methods of contraception mentioned above during study period and at least 120 days after the last dosing of FB825.

⁃ The subject has a body weight ≥ 40 kg at screening.

⁃ The subject has a normal or non clinically significant abnormal, as determined by the investigator, 12-lead electrocardiogram (ECG).

⁃ The subject is able to provide written informed consent.

⁃ The subject agrees to comply with all protocol requirements.