Ankylosing spondylitis is a chronic immune-mediated disease affecting the sacroiliac joints and the spine manifesting with new bone formation and osteopenia. Over the past decade, tumour necrosis factor alpha (TNF-α) inhibitors (TNFi) have become the cornerstone for therapy in improving functional outcomes, and decreasing disease activity in patients with a marginal benefit from non-steroidal anti-inflammatory (NSAID) therapy. At this time, it remains to be determined whether these agents decrease new bone formation, although some studies have recently suggested that. Areas covered: In this review we discuss the factors that favour a good response to these agents both initially and during maintenance, and some of the more recent studies outlining strategies for dose reduction. Expert commentary: Finally, we discuss the importance of using more objective tools for disease activity, such as magnetic resonance imaging, as a complementary tool for clinical assessments in both predicting responses to treatment but also in selecting patients most suited for targeted therapy.