Anti-TSLP (AMG 157) Plus Antigen-Specific Immunotherapy for Induction of Tolerance in Individuals With Cat Allergy

Inclusion Criteria: * History of moderate-severe allergic rhinitis caused by cat exposure for at least 2 yrs * Skin prick test wheal \>/=5 mm to standardized cat extract * Immunoglobulin E (IgE) \>/=0.7 kU/L (class 2) to cat extract * Screening nasal allergen challenge in which: \*TNSS is \</= 3 after the 0 concentration (vehicle control only) dose, * TNSS increase is \</=1 from the TNSS prior to allergen administration to the TNSS after the 0 concentration (vehicle control only) dose, * TNSS is \>/=8 after the highest dose, and * Between the first non-zero dose and 10 minutes after the highest dose,either: * \>/=3 sneezes are counted or * \>20% drop in PNIF is recorded * Body mass index (BMI) between 1 and 32 kg/m\^2, inclusive at screening * Clinically acceptable physical examination and electrocardiogram (ECG) results (12-lead reporting RR, PR, QRS, QT and QTcF) prior to Day 0 based on the opinion of the investigator * Adequate renal function (defined by creatinine clearance \>80 mL/min using the Cockcroft Gault equation) * For women of childbearing age, a willingness to use a highly effective form of contraception for five months after last dose of study medication. Highly effective methods of birth control include abstinence, vasectomy by the male partner, or a condom with spermicide in combination with either hormonal birth control, IUD or barrier methods used by the woman. * For men with female partners of childbearing potential, agreement not to donate sperm and to inform their female partner of their participation in this clinical study and use highly effective methods of birth control for five months after last dose of study medication. Highly effective methods of birth control include abstinence, vasectomy, or a condom with spermicide in combination with either hormonal birth control, Intrauterine device (IUD) or barrier methods used by the woman. * The ability to give informed consent and comply with study procedures Exclusion Criteria: * Prebronchodilator Forced Expiratory Volume at one second (FEV1) less than 0% of predicted value at screening visit * History of moderate or higher Allergic Rhinitis and its Impact on Asthma (ARIA) severity classification for allergic rhinitis in the last year due to allergens other than cat * History of asthma meeting the National Asthma Education and Prevention Program (NAEPP) Expert Panel Report 3 (EPR3) classification of mild-persistent or worse in the past year, other than with cat exposure, requiring regular inhaled corticosteroids for \>4 weeks per year * History of serious chronic medical conditions which might interfere with treatment or assessments * History of emergency visit or hospital admission for asthma in the previous 12 months * History of chronic obstructive pulmonary disease (COPD) * History of significant recurrent acute sinusitis, defined as 2 episodes/yr for the last 2 years, all of which required antibiotic treatment * History of chronic sinusitis, defined as a sinus symptoms lasting \>12 weeks that includes \>/=2 major factors or 1 major factor and 2 minor factors. Major factors are defined as facial pain or pressure, nasal obstruction or blockage, purulent or discolored postnasal discharge, purulence in nasal cavity, or impaired or loss of smell. Minor factors are defined as headache, fever, halitosis, fatigue, dental pain, cough, and ear pain, pressure, or fullness. * History of systemic disease affecting the immune system such as autoimmune diseases, immune complex disease, or immunodeficiency, where, in the opinion of the study physician, participation in the trial would pose a risk or significant effect on the immune system * Diabetes (Type I or II) * Evidence of any active or suspected bacterial, viral, fungal or parasitic infection(s) within 30 days prior to randomization * High risk of parasitic disease as judged by the investigator * Positive QuantiFERON(R) tuberculin test UNLESS the potential subject has been treated with appropriate chemoprophylaxis * Exposure to an individual with active tuberculosis within six months from randomization * Subjects tested positive for HIV antibody, Hep B surface antigen, or Hep C antibody * At randomization, current symptoms of, or treatment for, upper respiratory tract infection, acute sinusitis, acute otitis media, or other relevant infectious process; serous otitis media is not an exclusion criterion. Participants may be re-evaluated for eligibility after symptoms resolve. * History of malignancy of any type, including basal cell and squamous cell cancers of the skin, within 5 years of enrollment * Tobacco smoking (ANY) within the last year or a history of \>/=10 pack years * Previous immunotherapy treatment with cat allergen within the previous 10 yrs * Any history of grade 4 anaphylaxis due to any cause as defined by the CTCAE grading criteria for immunotherapy * History of bleeding disorders or treatment with anticoagulation therapy * Treatment with omalizumab within 6 months prior to randomization * Currently taking any of the following medications: beta blockers; tricyclic antidepressants; monoamine oxidase inhibitors; or anti-IgE monoclonal antibody treatment * Ongoing systemic immunosuppressive treatment * History of intolerance to the study therapy, rescue medications, or their excipients * For women of childbearing age a positive serum or urine pregnancy test with sensitivity of \<50 mIU/mL within 72 hours before the start of study therapy * The use of any investigational drug within 6 months of randomization * The presence of any medical condition that the investigator deems incompatible with participation in the trial.