Antigenicity Results At the time of this interim report, 134Avonex@treated subjects had at least one sample drawn for binding antibody testing. At Month 12; 13.6% of subjects had binding antibodies to interferon beta andat Month 21,23.1% of subjects had binding antibodies to interferon beta. At the time of this interim report, 150AvonexGWreated subjects had at least one sample drawn for neutrahzing antibody testing. Of these 150 subjects, 8 (5.3%) hadtiters X for anti-interferon beta serum neutralizing activity at some time during the course of the study. Of these 8 subjects, 5 subjects (3.3%) hadtiters that were 220 (and
therefore, also 25). Three subjects hadtiters between 5 and 20. The percentage of subjects testing positive for neutralizing antibodies did not change substantially after Month 15through Month 21, consistent with perhapshaving reacheda plateau in the incidence of neutralizing antibodies. However, the numbers of subjects tested at Months 18 and 21were much smaller than the numbers tested prior to that time, and the incidence of binding antibodies continued to increaseat Month 21 as compared to Month 12. Antibody results beyond Month 21 arenot contained in this report. The results of the assaysfor neutralizing antibodies are summarized below in Table.1.
Table 1: Incidence of Neutralizing Antibodies
Nlnbi!r of = N = t s ! l i x t e d ( a )