Abstract text (incl. figure legends and references)

Question. Is a monoclonal antibody (MAB) against circulating CGRP (calcitonin gene related peptide) effective in chronic migraine (CM) patients who did not respond at all or sufficiently to a MAB against CGRP receptor?

Methods. This is a prospective audit conducted at the Headache Centre at Guy"s and St Thomas" Hospital. We collected demographic and clinical data on patients who were exposed and eventually discontinued erenumab and were subsequently switched to fremanezumab. The main outcomes of this analysis include percentage of responders to Fremanezumab (reduction of monthly migraine days of at least 30% compared to baseline) as per NICE UK guidance at month 3 and 6.

Results. Their demographic and clinical details of the 33 patients included are reported in Table 1. Patients received a median of 15 (IQR = 7-21) erenumab injections. After discontinuing erenumab, patients received the first dose of fremanezumab after a median of 14 (IQR 6-54) weeks. After 3 months of treatment with fremanezumab, 25 patients (75.8%) were not responders, while 8 patients (24.2%) were responders. Their response was sustained at month 6. Of the non-responders at month 3, 16 patients discontinued the treatment, nine patients continued until month 6 and two of them became responders at month 6. Non-responders to erenumab and fremanezumab tried further treatments (Figure 1).

Conclusions. Our preliminary analysis showed that 24.2% of CM patients who fail to respond to erenumab, can respond to fremanezumab. Furthermore, a small proportion of patients who did not respond to Fremanezumab at month 3 but continued to month 6, became responders (22%), increasing the overall percentage of responders to 30.3% after 6 months of treatment. Our initial data suggests that switching from a MAB against CGRP receptor to a MAB against circulating CGRP may have a beneficial effect in a subgroup of otherwise refractory patients.