AstraZeneca is to acquire Amolyt Pharma in a deal potentially worth more than $1 billion.
The pharmaceutical giant will pay $800m upfront, with a further $250m payable to Amolyt shareholders "upon achievement of a specified regulatory milestone".
The deal will be subject to regulatory approval, and is expected to close by the end of September.
AstraZeneca said the acquisition would boost its rare disease treatment division, Alexion.
Amolyt specialises in rare endocrine disease treatments.
It is currently testing treatments for conditions to treat hypoparathyroidism - a rare hormonal deficiency thought to affect around 115,000 people in the US and 107,000 people in the European Union.
"Chronic hypoparathyroid patients face a significant need for an alternative to current supportive therapies, which do not address the underlying hormone deficiency," said Marc Dunoyer, CEO of Alexion. "As leaders in rare disease, Alexion is uniquely positioned to drive the late-stage development and global commercialisation of eneboparatide, which has the potential to lessen the often debilitating impact of low parathyroid hormone and avoid the risks of high-dose calcium supplementation.
"We believe this programme, together with Amolyt's talented team, expertise and earlier pipeline, will enable our expansion into rare endocrinology."
"We enthusiastically welcome the proposed acquisition of Amolyt by AstraZeneca, an organisation that shares our dedication to delivering life-changing treatments to people living with rare diseases," said Thierry Abribat, CEO of Amolyt Pharma. "This agreement offers the opportunity to meaningfully advance our pipeline therapies.
"Strong Phase II data suggest eneboparatide has the potential to improve outcomes for patients and to shift the treatment paradigm for hypoparathyroidism, and we look forward to seeing the continued advancement of the Phase III trial."
AstraZeneca is headquartered in England, while Amolyt Pharma is based in France.
