Pfizer will sell down its stake in Haleon, the consumer healthcare unit of GSK, after its listing in London planned for later this month, GSK said on Wednesday.

That indicates a change of heart on the part of the U.S. pharma giant, which owns 32% of the group behind such brands as Voltaren joint pain cream and Sensodyne toothpaste. GSK had said earlier this year when it announced the spin-off plan, that Pfizer would hold on to its shares and have representation on its board.

The news creates an unwelcome stock hangover effect for GSK as it prepares for a deal that it hopes will lighten its balance sheet and sharpen its focus on cancer and immunology drugs. The U.K. company said, however, that Pfizer had agreed to reduce its stake in “a disciplined manner” under a marketing agreement with GSK, after a lockup period of “several months”.

Under the terms of the demerger plan, GSK will keep a stake of around 6% in Haleon for now but it intends to monetize that in due course, to fund its future investments in developing or buying new drugs. Another 7.5% stake will be held by mechanisms to support its pension plan, while GSK shareholders will receive shares accounting for just under 55% of the company.

Under pressure from activist investor Elliott Management, GSK chief executive Emma Walmsley has decided to shed the cash-generative but staid business to pursue the higher valuations typically enjoyed by companies that specialize in developing new drugs. Walmsley rejected an offer of 50 billion pounds ($63 billion) from Unilever (NYSE:UL) earlier this year as too low, stressing that it expects organic sales growth of between 4% and 6% in the medium term.

GSK’s new focus was evident earlier this week in its acquisition of U.S.-based vaccine specialist Affinivax for up to $3.3 billion. It also agreed to pay $1.9 billion for Sierra Oncology in April, as previously reported.

GSK stock was up 0.1% by 8:40 AM ET (1240 GMT) in London trading, while Pfizer stock was up 0.2%.