Editors' pick: Originally published April 6.

Allergan(AGN) - Get Report CEO Brent Saunders, the drug industry's biggest and best dealmaker, might be back in the game.

The proposed $150 billion merger of Allergan and Pfizer(PFE) - Get Report  was scuttled on Wednesday, in the wake of new U.S. Treasury rules unveiled Monday night aimed at preventing tax-avoiding inversion deals. Allergan shares fell 22% soon after the Treasury news broke.

Saunders could start shopping again for biotech and smaller pharma companies to fuel Allergan's growth, just like he did before the Pfizer deal. He'd have plenty of cash to fund new acquisitions, assuming the $40 billion sale of Allergan's generics business to Teva closes later this year. On top of that cash pile, Allergan could receive a breakup fee from Pfizer of $400 million, minimum. The breakup fee could rise to as much as $3.5 billion, depending on how the merger is terminated.

Not that Saunders needs help or motivation to close deals, but he could look to Shire(SHPG) - Get Report CEO Flemming Ornskov for inspiration. AbbVie(ABBV) - Get Report paid a $1.7 billion breakup fee to Shire in 2014 after the U.S. Treasury enacted stricter inversion rules. Soon after, Shire's Ornskov used the AbbVie money to help finance a $5 billion acquisition of NPS Pharma and is now in the process of closing on a $32 billion takeover of Baxalta (BXLT) .

Which biotech and drug companies would be in Allergan CEO Saunders' sight as potential acquisition targets?

Let's start with the most ironic of options: Valeant Pharmaceuticals (VRX) . Given Valeant's myriad accounting issues and mountain of debt at risk of default, Saunders could -- and should -- probably wait to pick up Valeant's best assets in a fire sale or bankruptcy. Think the Salix drugs which treat stomach disorders.

Allergan might be interested in acquiring Valeant's Bausch & Lomb eye care unit. [Bill Ackman has said Valeant could sell Bausch & Lomb to raise money].

Allergan differs from Valeant in that Saunders believes there's value in spending money on research and development of new drugs -- within reason. If he wants to go big into drug development and bolster earnings today, Biogen(BIIB) - Get Report or Abbvie would make intriguing targets.

Investors surveyed by Evercore ISI last summer mentioned Biogen and AbbVie as smart takeover bait for Allergan, according to a profile of Saunders written by Forbes' Matt Herper.

For the same reasons, Saunders could use Allergan's financial muscle to buy Celgene(CELG) - Get Report , Bristol-Myers Squibb(BMY) - Get Report or AstraZeneca(AZN) - Get Report .

Sure, all of these deal would be expensive, but then transformational acquisitions don't come cheap.

Might Saunders be interested in acquiring Revance Therapeutics(RVNC) - Get Report , a competitor to Allergan's Botox business? He could also bolster Allergan's existing dermatology business with purchases of Anacor Pharma (ANAC) or Dermira(DERM) - Get Report .

Saunders could also look for multiple, smaller specialty pharma deals to grow Allergan. Here's a starter list: Jazz Pharma(JAZZ) - Get Report , Depomed (DEPO) , Endo International(ENDP) - Get Report and Amag Pharma(AMAG) - Get Report .

There's one more thing to consider: Pfizer will likely be a motivated buyer of biotech and drug assets with Allergan removed from the picture. Let the bidding wars begin!

Allergan and Biogen are holdings in Jim Cramer's Action Alerts PLUS portfolio.

Adam Feuerstein writes regularly for TheStreet. In keeping with company editorial policy, he doesn't own or short individual stocks, although he owns stock in TheStreet. He also doesn't invest in hedge funds or other private investment partnerships. Feuerstein appreciates your feedback; click here to send him an email.