Exhibit 15.3



NOTIFICATION OF TRANSACTIONS OF DIRECTORS, PERSONS DISCHARGING MANAGERIAL RESPONSIBILITY OR CONNECTED PERSONS



This form is intended for use by an issuer to make a RIS notification required by DR
3.1.4R(1).



|(1) | An issuer making a notification in respect of a transaction relating to the shares or debentures of the issuer should complete boxes 1 to 16, 23 and 24.
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|(2) | An issuer making a notification in respect of a derivative relating the shares of the issuer should complete boxes 1 to 4, 6, 8,13, 14, 16, 23 and 24.
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|(3) | An issuer making a notification in respect of options granted to a director/person discharging managerial responsibilities should complete boxes 1 to 3 and 17 to 24.
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|(4) | An issuer making a notification in respect of a financial instrument relating to the shares of the issuer (other than a debenture) should complete boxes 1 to 4, 6, 8, 9, 11, 13, 14,
16, 23 and 24.
|--- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------



Please complete all relevant boxes should in
block capital letters.



1. Name of the issuer



CAMBRIDGE ANTIBODY TECHNOLOGY GROUP PLC



2. State whether the notification relates to (i) a transaction notified in accordance
with DR 3.1.4R(1)(a); or



(ii) DR 3.1.4(R)(1)(b) a disclosure made in
accordance with section 324 (as extended by section 328) of the Companies Act 1985; or



(iii) both (i) and (ii)



(ii)



3. Name of person discharging managerial responsibilities/director



DIANE MELLETT



4. State whether notification relates to a person connected with a person discharging managerial responsibilities/director named in 3 and
identify the connected person AS IN 3 ABOVE



5. Indicate whether the
notification is in respect of a holding of the person referred to in 3 or 4 above or in respect of a non-beneficial interest AS IN 3 ABOVE



---

6. Description of shares (including class), debentures or derivatives or financial instruments relating to shares



ORDINARY 10 PENCE SHARES



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



GREENWOOD NOMINEES LIMITED



8. State the nature of the transaction



SALE OF SHARES FOLLOWING EXERCISE OF OPTION REPORTED ON 25
NOVEMBER 2005



9. Number of shares, debentures
or financial instruments relating to shares acquired



NIL



10. Percentage of issued class acquired (treasury shares of that
class should not be taken into account when calculating percentage)



NIL



11. Number of shares, debentures or
financial instruments relating to shares disposed



4,696



12. Percentage of issued class disposed (treasury shares of
that class should not be taken into account when calculating percentage)



0.009%



13. Price per share or value of
transaction



GBP 6.74



14. Date and place of transaction



28 NOVEMBER 2005

LONDON



15. Total holding following notification and total percentage holding following notification (any treasury shares should not be taken into account when calculating
percentage)



17,963

0.034%



16. Date issuer informed of transaction



28 NOVEMBER 2005



If a person discharging managerial responsibilities has been granted options by the issuer complete the following boxes



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17. Date of grant



_________________________________________



|18. | Period during which or date on which it can be exercised
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_________________________________________



|19. | Total amount paid (if any) for grant of the option
|--- | --------------------------------------------------



_________________________________________



|20. | Description of shares or debentures involved (class and number)
|--- | ---------------------------------------------------------------



_________________________________________



|21. | Exercise price (if fixed at time of grant) or indication that price is to be fixed at the time of exercise
|--- | ----------------------------------------------------------------------------------------------------------



_________________________________________



|22. | Total number of shares or debentures over which options held following notification
|--- | -----------------------------------------------------------------------------------



_________________________________________



23. Any additional information



ON 25 NOVEMBER 2005 THE COMPANY REPORTED THAT DIANE MELLETT HAD EXERCISED AN OPTION OVER 7597 SHARES IN THE COMPANY AND THAT THE 25 NOVEMBER 2005 WAS THE FINAL DAY THAT THE OPTION COULD BE EXERCISED BEFORE IT WOULD
IRREVCOCABLY LAPSE. ON 28 NOVEMBER 2005 DIANE MELLETT SOLD SUFFICIENT SHARES TO PAY THE EXERCISE COST AND OTHER COSTS ASSOCIATED WITH THAT OPTION EXERCISE



24. Name of contact and telephone number for queries



JUSTIN HOSKINS

01223 898 589



Name and signature of duly authorised officer of issuer responsible for making notification



JUSTIN HOSKINS, COMPANY SECRETARY



Date of notification



28 NOVEMBER 2005



END