GALAPAGOS

Initial reference price: will be the definitive offer price that will be determinated on 04-05-2005 after 4 p.m. and published in the financial press on 6 May 2005 before opening of the markets. Thresholds of listing: As provided in the ETA Nr 2004-433 dated 20 September 2002, the static price range will be set at +/-20% around the reference price. If the price is outside the static price range the stock will be reserved during 15 minutes. The new reference price used will be the treshold (up or down) reached previously. The static price range will be set at +/-10% of this new reference price. This procedure will be repeated until an opening price will be established. At the opening of the security, the opening price will be the new reference price with a static price range of +/-10% and a dynamic price range of +/-5%. Usual trading rules in term of thresholds and of reservation period will be applied. When Issued: according to the terms of the offering described in the prospectus, investors have to be aware that the offered shares must be delivered on 10 May 2005. Euronext Brussels has indicated that it will cancel all transactions realized on the regulated market Eurolist by Euronext Brussels if the offered shares are not delivered on 10 May 2005. The attention of the public is drawn upon the fact that, from the first listing of the shares on the regulated market Eurolist by Euronext Brussels and until 10 May 2005, it has to take into account the eventuality as described above for every operation that it intends to realise through Euronext or over the counter.