Activist investor William Ackman and Canadian company Valeant Pharmaceuticals established a joint venture with an eye towards acquiring botox maker Allergan, according to a securities filing Monday. Ackman's fund, Pershing Square Capital Management, and Quebec-based Valeant, acquired 28.9 million shares of Allergan, or 9.7 percent of the company. "Valeant currently intends to propose a merger in which (Allergan) will receive a combination of cash and Valeant common shares," Valeant said in the filing to the US Securities and Exchange Commission. Valeant has not finalized an offer, but estimated the cash component of the bid would be around $15 billion, the filing said. Allergan's market capital was $42.4 billion at the market close Monday. "Although Valeant currently expects to make an offer, it is under no obligation and provides no assurance it will do so," the company added. Founded in 1948, Allergan is best known for marketing the anti-ageing medication botox, which is injected into muscles.\\ Valeant has completed more than a dozen acquisitions over the last 18 months in a speedy growth campaign. The company's biggest deal by far was an $8.7 billion purchase of US eye-health company Bausch & Lomb. Allergan shares jumped 6.0 percent to $142 Monday. Shares then rose an additional 20.4 percent to $171.03 in after-hours trading.