Study Data Confirms That Patients Treated With Rebif(R) Are More Likely to Remain Free of Relapses D

"It is very clear from this data that the treatment benefit of Rebif(R) over Avonex(R) in preventing the occurrence of relapses is maintained for 48 weeks," said Dr. Panitch. "This is a highly significant result for physicians and patients in the treatment of multiple sclerosis".

The primary endpoint of the EVIDENCE study was based on a comparison of the proportion of patients who did not experience a relapse of MS at 24 weeks. Over 48 weeks, 62% of patients who received Rebif(R) did not have a relapse compared to 52% of Avonex(R) treated patients, a statistically significant difference (p=0.009). Rebif(R) patients had a 19% relative increase in remaining free of relapses over the 48 weeks compared to Avonex(R) patients. The comparative figure during the first 24 weeks was also 19% in favor of Rebif(R).

Rebif(R) patients had a 30% reduction in the rate of occurrence of first relapse during the 48 weeks relative to Avonex(R) patients (p<0.003).

The main MRI endpoint of the study over 48 weeks was an assessment of brain lesions as measured by T2 weighted magnetic resonance imaging (MRI) scans. Patients taking Rebif(R) had significantly fewer active lesions per scan (0.9) than patients taking Avonex(R) (1.4). This relative reduction of 36% in favor of Rebif(R) is a highly statistically significant difference (p<0.001). The exact relationship between MRI findings and the clinical status of patients is unknown.

Below is a summary of the main EVIDENCE study data:

EVIDENCE DATA Rebif(R) Avonex(R) Relative difference P value 44mcg 30mcg in favor 3x weekly 1x weekly of Rebif(R)

Number of patients 339 338

Treated for 48 weeks 314 (93%) 317 (94%)

Proportion Relapse-Free (primary endpoint) At 24 weeks 75% 63% 19% <0.001 At 48 weeks 62% 52% 19% 0.009

Rate of occurrence of first relapse throughout Hazard Ratio 48 weeks 0.7* 30% 0.003

Mean (median) number of MRI combined unique active lesions per scan (main secondary endpoint) At 24 weeks 0.17 (0.8) 0.33 (1.2) 50% (33%) <0.001

Mean (median) number of MRI T2 active lesions per scan At 48 weeks 0.9 (0.0) 1.4 (0.5) 36% <0.001

Proportion of patients with no T2 active lesions 63% 45% 40% <0.001

*The hazard ratio (0.7) is the ratio of the rates of occurrence of first relapse for Rebif patients compared to Avonex patients. Given that any patient was relapse free up to a particular timepoint during 48 weeks, the rate of occurrence of first relapse for that patient is the probability of that patient having their first relapse at the very next timepoint.

A comparison of safety based on the EVIDENCE study 48-week results indicates that both Rebif(R) and Avonex(R) are associated with a similar overall side effect profile, including flu like symptoms, headache, fatigue and muscle ache that occur in about half of the patients treated. Consistent with the higher and more frequent dose of interferon used in Rebif(R) therapy, certain side effects were observed in significantly greater number of patients on Rebif(R) than on Avonex(R): injection site reactions (83% vs 28%), liver function disorders (18% vs. 9%), and changes in white blood cell counts (11% vs. 5%). These side effects had little impact on the ability of patients to continue on Rebif(R) therapy, and no significant difference was seen in the proportion of patients who stopped therapy due to the events (5% vs 3%). When considering severe side effects, no difference between patients taking Rebif(R) and Avonex(R) was seen. Moreover, the total proportions of patients who remained on therapy were very similar, with 93% of Rebif(R) patients and 94% of Avonex(R) patients completing 48 weeks of treatment.

The effect of neutralizing antibodies on the efficacy of treatment with interferon beta-1a is unknown(2). In the EVIDENCE trial, the development of neutralizing antibodies did not have any observable clinical impact and did not affect Rebif(R)'s superiority over Avonex(R) in the primary endpoint of preventing relapses.

The EVIDENCE study is the largest prospective, randomized comparative study of two disease modifying drugs in RRMS to date. The open-label, assessor-blinded study included 677 patients with RRMS who had not been treated with interferon before, ages 18-55, at 56 centers in the US, Canada and Europe. Patients underwent repeated clinical and MRI assessments while taking either Rebif(R) (44 mcg three times weekly, subcutaneously) or Avonex(R) (30 mcg once weekly, intramuscularly). During the study, assessing neurologists and radiologists were blinded from knowing which drug the patients were taking.

Additional Product Information

Rebif(R) was approved in Europe in 1998 and is registered for use in more than 70 countries worldwide. During 2001, Rebif(R) increased its leading position in these countries as the treatment of choice for patients with relapsing forms of MS with a market share of 38% in value terms and sales of $379.6m outside the US.

The EVIDENCE study was pivotal to the market approval of Rebif(R) by the US Food and Drug Administration on March 07, 2002 under the terms of the Orphan Drug Act. Rebif(R) is approved in the US for the treatment of patients with relapsing forms of multiple sclerosis to decrease the frequency of clinical exacerbations and delay the accumulation of physical disability.

People living in the US with relapsing forms of MS can find more information about Rebif(R) in the full prescribing information, on line at http://www.rebif.com/ or by calling MS LifeLines at 1-877-44REBIF. Patients should be instructed to read the Medication Guide accompanying the product.

Conference Call and Webcast

Serono will hold a conference call to discuss its First Quarter 2002 Results and the EVIDENCE study 48 Week data on Tuesday, April 23, 2002, at 10:00 am Eastern Standard Time and 16.00 pm Central European Time. To join the telephone conference, please dial 412 858 4600 (from the US), 91 610 41 11 (from Europe), and 091 610 41 11 (from Switzerland). Telephone playback will be available one hour after the conference call and until Thursday, April 25, 5 pm Central European Time. To access this playback please dial the following numbers 412 858 14 40 (from the US) 91 610 2500 (from Europe) and 091 610 25 00 (from Switzerland) and enter the PIN code 347# from a touch tone telephone.

The event will also be relayed by live webcast which interested parties may access via Serono's USA affiliate. Please go to http://www.seronousa.com/ , click on the related ticker announcement, and follow the instructions. The webcast will be available for replay until close of business on May 07, 2002.

Some of the statements in this press release are forward looking. Such statements are inherently subject to known and unknown risks, uncertainties and other factors that may cause actual results, performance or achievements of Serono S.A. and affiliates to be materially different from those expected or anticipated in the forward-looking statements. Forward-looking statements are based on Serono's current expectations and assumptions, which may be affected by a number of factors, including those discussed in this press release and more fully described in Serono's Annual Report on Form 20-F filed with the U.S. Securities and Exchange Commission on April 23, 2001. These factors include any failure or delay in Serono's ability to develop new products, any failure to receive anticipated regulatory approvals, any problems in commercializing current products as a result of competition or other factors, our ability to obtain reimbursement coverage for our products, and government regulations limiting our ability to sell our products. Serono has no responsibility to update the forward-looking statements contained in this press release to reflect events or circumstances occurring after the date of this press release.

About Serono

Serono, Inc., located in Rockland, MA, is the US affiliate of Serono, S.A., a global biotechnology leader, headquartered in Geneva, Switzerland. The Company has six recombinant products on the market, Gonal-F(R) (follitropin alfa for injection), Luveris(R) (lutropin alfa), Ovidrel(R)/Ovitrelle(R) (choriogonadotropin alfa for injection), Rebif(R) (interferon beta-1a), Serostim(R) [somatropin (rDNA origin) for injection] and Saizen(R) [somatropin (rDNA origin) for injection]. (Luveris(R) is not approved in the USA).(3) In addition to being the world leader in reproductive health, Serono has strong market positions in neurology, metabolism and growth. The Company's research programs are focused on growing these businesses and on establishing new therapeutic areas. Currently, there are fifteen new molecules in development.

In 2001, Serono achieved worldwide revenues of US$1.38 billion, and a net income of US$317 million, making it the third largest biotech company in the world based on revenues. The Company operates in 45 countries, and its products are sold in over 100 countries. Bearer shares of Serono S.A., the holding company, are traded on the virt-x (SEO) and its American Depositary Shares are traded on the New York Stock Exchange (SRA).

(1) EVIDENCE: Evidence for Interferon Dose-response European-North American Comparative Efficacy. See Rebif(R) full prescribing information at http://www.rebif.com/ .

(2)Goodin DS, Frohman EM, Garmany GP, et al. Disease Modifying Therapies in Multiple Sclerosis. Report of the Therapeutics and Technology Assessment Subcommittee of the American Academy of Neurology and the MS Council for Clinical Practice Guidelines. Neurology 2002; 58: 169-178, 175.

(3) Package inserts for the company's US products are available at http://www.seronousa.com/ or by calling 1-888-275-7376.

For more information, please contact:

Media Relations Serono, Inc., Rockland, MA Tel: 781 681 2340 Fax: 781 681 2935 www.seronousa.com

Media Relations Serono, Geneva, Switzerland: Tel: 22 739 36 00 Fax 22-739 30 85 www.serono.com

Investor Relations MontRidge, LLC Tel: 203 894 8038 Fax: 203 894 8039

Feinstein Kean Healthcare Media Relations Tel: 617 761 6791 Fax: 617 577 8985 www.fkhealth.com

Investor Relations Serono, Geneva, Switzerland: Tel: 22 739 36 01 Fax : 22 739 30 22 www.serono.com
Contact: Serono Media Relations: +1-781-681-2340, or Media Relations

Serono, Geneva, Switzerland: 22 739 36 00; or MontRidge, LLC Investor

Relations: +1-203-894-8038; or Feinstein Kean Healthcare Media Relations,

+1-617-761-6791

Website: http://www.serono.com/