DUBLIN - Ireland's Allergan Plc, the maker of Botox, has entered into a definitive agreement to acquire Kythera Biopharmaceuticals Inc in a cash and equity transaction valued at $75 per Kythera share, or around $2.1 billion, to expand its portfolio of aesthetics treatments.

The $75 per share offer price represents a premium of 23.5 percent to Kythera's Tuesday close.

The fixed-value transaction will be payable 80 percent in cash and 20 percent in new AGN shares issued to Kythera shareholders, stated Allergan in a statement Wednesday.

"Allergan's 2015 earnings-per-share forecast provided on May 11, 2015 is unchanged as a result of the acquisition, which is expected to breakeven in 2016 and be accretive thereafter. The company remains committed to de-levering to below 3.5x debt to Adjusted EBITDA by the end of the first quarter of 2016," Dublin headquartered Allergan stated.

An industry leader in research and development, Allergan markets a portfolio of treatments for the central nervous system, eye care, medical aesthetics, gastroenterology, women's health, urology, cardiovascular and anti-infective therapeutic categories. It also operates the world's third-largest global generics business, providing patients around the globe with increased access to affordable, high-quality medicines. ,

Acquisition of Kythera will add a strong facial aesthetics portfolio and provide Allergan access to Kybella, the first and only approved non-surgical treatment to reduce fat under the chin, or what is known as double chin, the companies said

"The acquisition of Kythera is a strategic investment that strengthens our leading global position in aesthetics and continues to position us for long-term growth," said Brent Saunders, CEO and President of Allergan.

"Kybella is an exciting new product that offers patients the first and only clinically-proven, non-surgical treatment for submental fullness (excess fat under the chin). As a leader in aesthetics, we know our customers are looking to offer their patients new options beyond traditional facial aesthetics."

Shares of Allergan gained 0.5 percent to $299.47, while Kythera Biopharmaceuticals jumped 22 percent to $74 on Wednesday, close to Allergan's offer price.

Allergan's acquisition of Kythera is subject to approval by its shareholders, and fulfillment of other conditions. Allergan currently anticipates closing the transaction in the third quarter of 2015.

This is Allergan's first multi-billion acquisition since its takeover by Ireland based Actavis Plc for $66 billion. Post the acquisition in November last year, Actavis adopted the Botox-maker's name on June 15.

Kythera's CEO, Keith Leonard expressed his eagerness in working along with Allergan in launching Kybella, both in the US as well as foreign markets.

Kybella is expected to earn at least $500 million, and is likely to generate around same amount in international sales.

Allergan believes that the transaction will not have any immediate effect on results for 2015 but will begin adding to earning per share after 2016.