The purpose of this study is to assess the safety and tolerability of gpASIT+TM administered subcutaneously in absence or in presence of an immunoregulating adjuvant in grass pollen allergic patients.

Inclusion Criteria:

• Subject has given written informed consent

• Age between 18 and 50 years

• The subjects are in good physical and mental health according to his/her medical history, vital signs, and clinical status

• Male or non pregnant, non-lactating female

• Females unable to bear children must have documentation of such in the CRF (i.e. tubule ligation, hysterectomy, or post menopausal (defined as a minimum of one year since the last menstrual period))

• Allergy diagnosis:

  • A history of seasonal allergic rhinoconjunctivitis (SAR) during the grass pollen season during at least during the two previous years
  • A positive skin prick test (wheal diameter ≥ 3 mm) to grass-pollen mixture
  • Specific IgE against grass pollen (RAST class 2 or IgE > 0.7 kU/l)
  • Asymptomatic to perennial inhalant allergens even if shown to be hypersensitive in a skin prick test.

Exclusion Criteria:

• Subjects with current or past immunotherapy (any time in the past)
• A history of hypersensitivity to the excipients
• Subjects requiring control medication against asthma (bronchodilator nebulised drugs or local or systemic corticosteroids)
• Subjects with documented evidence of acute or significant chronic sinusitis (as determined by investigator)
• Subjects with a history of hepatic or renal disease
• Subjects symptomatic to perennial inhalant allergens
• Subjects with rhinitis medicamentosa, non-specific rhinitis (to food dye, preservative agent…)
• Subject with malignant disease, autoimmune disease (and family medical history of autoimmune disease)
• Any chronic disease, which may impair the subject's ability to participate in the trial (i.e. severe congestive heart failure, active gastric or duodenal ulcer, uncontrolled diabetes mellitus, etc…)
• Subjects requiring beta-blockers medication
• Chronic use of concomitant medications that would affect assessment of the effectiveness of the trial medication (e.g. tricyclic antidepressants)
• Subject with febrile illness (> 37.5°C, oral)
• A known positive serology for HIV-1/2, HBs antigen or anti-HCV antibodies
• The subject is immunocompromised by medication or illness, has received a vaccine, corticoids or immunosuppressive medications within 1 month before trial entry
• Receipt of blood or a blood derivative in the past 6 months preceding trial entry
• Regular consumption of corticoids (oral, topic or nasal) or of anti-histaminic drugs within 4 weeks preceding the trial
• Any consumption of corticoids (oral, topic or nasal) or of anti-histaminic drugs within 1 week preceding the trial
• Use of long-acting antihistamines
• Female subjects who are pregnant, lactating, or of child-bearing potential and not protected from pregnancy by a sufficiently reliable method (OCs, IUD)
• Any condition which could be incompatible with protocol understanding and compliance
• Subjects who have forfeited their freedom by administrative or legal award or who are under guardianship
• Unreliable subjects including non-compliant subjects, subjects with known alcoholism or drug abuse or with a history of a serious psychiatric disorder as well as subjects unwilling to give informed consent or to abide by the requirements of the protocol
• Subjects without means of contacting the investigator rapidly in case of emergency, or not able to be contacted rapidly by the investigator
• Participation in another clinical trial and/or treatment with an experimental drug within 1 month of trial start
• Subjects who participated to trial BTT-gpASIT003 and were in the treated groups