Table 12.

European patents protecting gemtuzumab ozogamicin, ado-trastuzumab emtansine and brentuximab vedotin

EP Patent	Claimed subject matter	Closest prior art	Why inventive?
EP0689845B1*	ADC with calicheamicin and hydrazine linker	EP0392384 discloses Calicheamicin succinimidyl derivatives conjugated to an antibody	Examiner accepted that “nothing in the prior art suggests that the use of the current linker system to bind calicheamicin to an antibody would yield conjugates having high immunoaffinity to the target, low toxicity and high antitumour activity.” (EP office action of May 11, 2001)
EP2283867B1	Trastuzumab maytansinoid conjugate for treatment of cancer over-expressing ErbB2	WO0069460 discloses trastuzumab, plus generally mentions combination therof with maytansine	Examiner accepted applicant's arguments of Nov 18, 2013, that (i) the specific selection of trastuzumab and maytansine would be novel over WO'460. In support of inventive step, applicant argued (ii) against Chari et al (1992), which discloses a murine anti-cancer ADC comprising a maytansinoid and an anti ErbB2 antibody as not being the closest prior art, and (ii) that it was surprising that trastuzumab retained its cytostatic activity in an ADC, and would not be degraded to a mere targeting device, thus leading to an ADC where the antibody and the toxin act in concert. Applicant had also argued that at the priority date, there was uncertainty regarding the therapeutic potential of immunoconjugates.
EP2353611B1	ADC with Pentapeptide linker plus auristatin	WO02088172 discloses pentapeptide linkers, and ADCs using them, but not auristatin	WO0208817 was the only prior art document, but although pre-filed, published after the priority date, and did thus not affect inventive step

^*expired