Daiichi's challenge to Seattle enters the legal realm

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Developing an antibody-drug conjugate is tough, and companies that get the balance between target, toxin and linker right can expect to be richly rewarded. They will also defend their position vigorously, as Seattle Genetics and Daiichi Sankyo showed yesterday. The two groups had signed a collaboration in 2008 to develop ADCs against a single, undisclosed tumour antigen, but this ended seven years later. Daiichi separately went on to develop the Her2-targeting ADC trastuzumab deruxtecan, which it this year licensed to Astrazeneca for a massive $1.35bn up front. Now it has emerged that Seattle claims that Daiichi had used a variation of the US company’s proprietary linker and other technology to develop trastuzumab deruxtecan. Seattle had been seeking redress using non-legal means, namely the terminated deal’s dispute resolution provisions, but yesterday the matter entered the legal realm, with Daiichi filing a complaint asking for declaratory judgement – something that Seattle claims amounts to circumventing the dispute resolution process it had been pursuing. Trastuzumab deruxtecan is expected to generate 2024 sales of $2.7bn, according to EvaluatePharma sellside consensus, making it the second-biggest expected launch of 2020, so there is plenty for Seattle to play for.

Ups and downs of antibody-drug conjugate (ADC) development
Company Bull Bear
Immunogen Deal with Roche led to the development of Kadcyla. Current ADC focus is on IMGN632, which uses a novel class of cytotoxic payload and is optioned to Jazz. Kadcyla linker tech had to be optimised by Roche. Immunogen's own lead, IMGN9013, was abandoned after a neurotoxicity scare.
Seattle Genetics Developed Adcetris. Enfortumab vedotin looks like its second successful ADC asset. Discontinuation of vadastuximab talirine shows struggles to diversify in ADCs. Trastuzumab deruxtecan represents a threat to company's claim to have the best ADC tech.
Immunomedics Developed sacituzumab govitecan, and succeeded in defeating a licensing approach from Seattle Genetics. Sacituzumab givotecan has subsequently faced long-running manufacturing problems, leading to a US complete response letter.
Daiichi Sankyo Developed trastuzumab deruxtecan, which it licensed to Astrazeneca for $1.35bn up front. Ownership of the tech behind trastuzumab deruxtecan is being challenged by Seattle Genetics.
Mersana Current ADC focus is on Dolaflexin polymer tech, to which the toxic payload is attached. Lead ADC project, XMT-1522, was abandoned after a clinical hold. 
ADC Therapeutics Current ADC focus is on novel class of PBD dimer toxins. Discontinued ADCT-502 after toxicity concerns. Cancelled Nasdaq IPO.
Source: company filings.

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