Inclusion criteria:

1. Diagnosis of ankylosing spondylitis, as defined by Modified New York Criteria for Ankylosing Spondylitis (26).
2. Maintained inflammatory activity for more than 12 weeks defined by:·Axial forms: BASDAI higher than or equal to 4 (0-10) and at least one of the following parameters:. Global assessment of the disease by the patient higher than or equal to 4 (On a scale 0-10). Spinal pain higher than or equal to 4 on a visual analogue scale (VAS). Increase in erythrocyte sedimentation rate (ESR) and/or CRP above the normality parameters established by the laboratory.·Peripheral forms: Arthritis or enthesitis higher than or equal to 1 site and at least one of the following:. Global assessment of the disease by the patient higher than or equal to 4 (on a scale 0-10). Increase in erythrocyte sedimentation rate (ESR) and/or CRP above the normality parameters established by the laboratory
3. Failure to treatment: Failure to at least 2 NSAIDs at maximum recommended dose during at least 3 months (or a shorter time in case of intolerance, toxicity or contraindication).·In cases of ankylosing spondylitis with peripheral joint involvement, salazopyrine should have been used at a dose of 2-3 g per day and/or methotrexate (15 mg/week) for 4 months (or a shorter time in case of intolerance, toxicity or contraindication). In case of oligoarticular or localized involvement in enthesis: lack of response, at the discretion of the investigator, to local infiltrations and/or synoviorthesis.
4. Be between 18-70 years of age
5. Negative result of a pregnancy test in serum in screening visit and in urine in baseline visit, done in all women, except those surgically sterilized and those who have at least one year of menopause.
6. Sexually active women of childbearing potential must use medically acceptable contraceptive methods, including oral, injectable or implantable contraceptive methods, intrauterine devices or properly used barrier contraception. A woman of childbearing potential is defined as one who is biologically capable of becoming pregnant. This includes women who are using contraceptives or whose sexual partners are either sterile or using contraceptives.
7. Men who are not surgically sterile should agree to use reliable contraceptive methods during the study.
8. Ability to reconstitute the drug and self-inject it or have a person who can do so.
9. Capability to understand and voluntarily give written informed consent that is signed and dated, before any specific procedure of the protocol is performed.
10. Ability to store injectable test article at 2º to 8º C.

Exclusion criteria:

1. Contraindications for treatment with anti-TNF
2. Complete ankylosis of spine
3. Onset of treatment with DMARDs in the 4 weeks prior to baseline (SSZ, MTX and HCQ are permitted if the administrated dose has been maintained stable in the 4 weeks prior to baseline). Furthermore, patients with a dose of prednisone >10 mg/d or equivalent or modified in the 2 weeks prior to the baseline visit, those in whose infiltration has been performed with intraarticlar corticosteroids has been performed in the 4 weeks prior to the screening visit and those who follow treatment with more than one NSAID in the 2 weeks prior to the baseline visit are excluded.
4. Previous treatment with other TNF inhibitors and other biological drugs

5. Abnormalities in hematology profiles defined by:

   • leukocytes lower than or equal to 3.5 x 10 exponent 9 /L
   • hemoglobin lower than or equal to 8.5 g/L or 5.3 mmol/L
   • hematocrit lower than or equal to 27%
   • platelets lower than or equal to 125 x 10 exponent 9 /L
   • serum creatinine higher than or equal to 175 mmol/L
   • aspartate aminotransferase and alanine aminitransferase higher than or equal to 2 times the upper limit of normality
6. Important concomitant medical conditions, such as:-Class III or IV congestive heart failure according to New York Heart Association classification-Uncontrolled arterial hypertension (defined as screening systolic blood pressure > 160 mm Hg or screening diastolic blood pressure > 100 mm Hg)-Myocardial infarction within 12 months of the screening visit or unstable angina-Severe pulmonary disease requiring hospitalization or oxygen therapy-Diagnosis of multiple sclerosis or other central nervous system demyelinating disease -Presence or history of confirmed blood dyscrasias-Cancer or history of cancer (other than resected cutaneous basal cell or squamous cell carcinoma)-Serious infection (infection requiring hospitalization and/or intravenous antibiotics) within 1 month of administration of test article administration or active infection at screening or history of recurrent or chronic infection-Open cutaneous ulcers-Patients with known chronic infections as positivity to HIV, hepatitis B surface antigen (HBsAg), or hepatitis C virus (HCV) -Active tuberculosis infection (local guidelines for appropriate screening and treatment of tuberculosis in the setting of anti-TNF therapy must be followed)- Any condition that, in the investigator's judgment, might cause this study to be detrimental to the subject
7. Pregnant or breast-feeding women
8. Past or current psychiatric illness that would interfere with the subject's ability to comply with protocol requirements or give informed consent.
9. Treatment with any live (attenuated) vaccine within 4 weeks prior to baseline.
10. History of alcohol or drug abuse that would interfere with the subject's ability to comply with protocol requirements.
11. Treatment with any investigational drug within 3 months of screening visit.