Biogen goes back to 1995 to grab mosunetuzumab

It might come as a surprise to all but the most avid readers of US regulatory filings that Biogen owns a significant stake in Roche’s anti-CD20 franchise, including Ocrevus. Investors were reminded of this 27-year-old arrangement yesterday when Biogen exercised an option to license the Swiss group’s anti-CD20 bispecific mosunetuzumab.

The deal has already enabled Biogen to collect billions from these products, including Rituxan, which since becoming the first ever MAb approved to treat cancer has generated cumulative sales of over $100bn. Biogen also collects cash on Gazyva and Ocrevus; it will now do so on mosunetuzumab, and could in future repeat the trick with other Roche assets, including glofitamab.

In a sense mosunetuzumab will help offset the declining cash Biogen gets from a share of Rituxan and Gazyva’s profits, which have been hit by biosimilars and other competitors. Still, by far the biggest contributor to Biogen’s CD20 revenue line will be royalties on the multiple sclerosis blockbuster Ocrevus; extrapolating from Evaluate Pharma consensus forecasts these might exceed $1bn over at least each of the next six years.

The fruit of Roche & Biogen's 27-year CD20 marriage ($m)
	2018	2020	2022e	2024e	2026e
The current arrangement…
Rituxan US sales	4,289	3,022	1,192	810	640
Gazyva US sales	195	312	399	561	697
Profit on Rituxan & Gazyva US sales	3,815	2,901	1,384	1,193	1,163
Biogen's share of the above	1,432	1,080	512	441	430
Biogen co-promotion profits on Rituxan in Canada	70	52	0	0	0
Ocrevus global sales	2,406	4,614	6,242	7,127	7,639
Biogen royalty on Ocrevus	478	845	1,124	1,283	1,375
Total booked by Biogen	1,980	1,978	1,636	1,724	1,805
…and possible future Roche products?
Mosunetuzumab global sales	0	0	68	248	525
Biogen has opted in to mosunetuzumab, and will receive a low to mid-30% US profit share plus low single-digit ex-US royalties
Glofitamab global sales	0	0	0	71	236
Glofitamab is wholly owned by Roche, but Biogen could negotiate a future opt-in
Source: Evaluate Pharma & SEC filings.

These forecasts have mosunetuzumab, which could be filed this year for follicular lymphoma, hitting 2026 sales of $525m, though the sellside sees $1bn at peak. Under the opt-in exercised yesterday Biogen paid $30m, and will contribute to development costs incurred in 2021, in return for a low to mid-30% share of US profits, plus a low single-digit ex-US royalty.

Though this might look like Biogen moving away from neurology and into oncology, the group has denied this to analysts. As such this is likely a financial exercise – seizing on a legacy tie-up to secure a large revenue line for a relatively small outlay.

But how did this all come about? For the answer you have to go back to 1995, when Idec Pharmaceuticals struck an anti-CD20 antibody discovery deal with Roche’s Genentech unit.

This originally focused on molecules coded Y2B8 and In2B8, which later became Zevalin, Idec’s radiolabelled anti-CD20 MAb that was the first US-approved radio-immunotherapy; and C2B8, which in Roche’s hands became the blockbuster Rituxan. In 2003 Idec underwent a $6.8bn merger with Biogen, assigning rights to the current Biogen entity.

Certain additional products

Meanwhile the deal underwent several amendments, perhaps the most significant of which was an expansion to include “certain additional products whose mechanism of action is initiated by interaction with CD20, including ... the humanised molecule created by Genentech known as G2H7”.

It is not clear whether G2H7 became Gazyva or Ocrevus, but either way Biogen now has rights to both of these. And now it owns a share of mosunetuzumab, a project that impressed at each of the last two Ash meetings, and one of the most promising bispecifics looking to push the increasingly competitive CD20 space forward once more.

Interestingly, mosunetuzumab is not the only late-stage anti-CD20 T-cell engaging MAb in development at Roche’s Genentech division; the other is glofitamab.

While mosunetuzumab uses a straight “1+1” format, glofitamab has a more complex “2+1” structure, with a silent Fc region to increase its half life. One question for Roche has been whether it would end up prioritising one asset over the other, though Biogen opting in to mosunetuzumab will probably not influence the Swiss group's thinking.

This is because the 1995 deal’s key amendment gives Biogen certain broad rights to anti-CD20 assets beyond “G2H7”, including “new products”, as well as a right of negotiation for third-party anti-CD20 products. Such assets might include glofitamab as well a RG6035, a brain-shuttle anti-CD20 in phase 1 for multiple sclerosis.

Roche said it was too early to speculate on RG6035, but confirmed to Vantage that Biogen "may have the opportunity to participate in the US commercialization of glofitamab, the details of which have yet to be negotiated".

https://www.evaluate.com/vantage/articles/news/deals/biogen-goes-back-1995-grab-mosunetuzumab