Holding(s) in Company

Cambridge Antibody Tech Group PLC
12 October 2005


                   NOTIFICATION OF MAJOR INTERESTS IN SHARES


1. Name of company

Cambridge Antibody Technology Group plc


2. Name of shareholder having a major interest

OrbiMed Advisors.


3. Please state whether notification indicates that it is in respect of holding
of the shareholder named in 2 above or in respect of a non-beneficial interest
or in the case of an individual holder if it is a holding of that person's
spouse or children under the age of 18

As in 2 above


4. Name of the registered holder(s) and, if more than one holder, the number of
shares held by each of them

OrbiMed Advisors LLC


5. Number of shares / amount of stock acquired

None


6. Percentage of issued class

None



7. Number of shares / amount of stock disposed

330,000 Ordinary shares
70,000 American Depositary Receipts


8. Percentage of issued class

0.774%


9. Class of security

Ordinary 10 pence shares


10. Date of transaction

30 August 2005


11. Date company informed

11 October 2005


12. Total holding following this notification

1,893,500 of which
1,667,400 are held in the form of ordinary 10 pence shares and
226,100 are held in the form of American Depositary Receipts


13. Total percentage holding of issued class following this notification

3.667%


14. Any additional information

Orbimed Advisors LLC has investment management discretion over the securities
held by the following entities:

Caduceus Capital Master Fund Limited
Caduceus Capital II, L.P.
UBS Eucalyptus Fund, L.L.C.
UBS Eucalyptus Fund, Ltd
HFR SHC Aggressive Master Trust
Knightsbridge Post Venture IV L.P.
Knightsbridge Integrated Holdings, V, LP
Knightsbridge Netherlands II, L.P.
Knightsbridge Integrated Holdings IV Post Venture, LP
Knightsbridge Post Venture III, LP
Knightsbridge Netherlands I LP
Knightsbridge Netherlands III - LP
Knightsbridge Integrated Holdings II Limited
Knightsbridge Venture Completion 2005, L.P.
Knightsbridge Venture Capital VI LP
Knightsbridge Venture Capital IV, L.P.
Knightsbridge Venture Capital III LP


15. Name of contact and telephone number for queries

Justin Hoskins 01223 898589


16. Name and signature of authorised company official responsible for making
this notification

Justin Hoskins, Company Secretary


Date of notification

12 October 2005


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for loss of business or loss of profits) arising in contract, tort or otherwise
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