The prominent short seller Andrew Left is at it again. And that means he's going long.

This time, he's focusing on the San Francisco genetic-testing company Invitae (NVTA - Get Report) . He says the stock price is due to explode. 

Invitae was trading up 1.4% to $27.56 after the Citron analyst published a note and placed a $100 price target on the stock. That's more than a tripling from the current level. 

The company has an "indestructible moat" around genetic testing, Left wrote.

Invitae "has now realized that genetic testing will become a cornerstone of healthcare and has taken a page out of the [Exact Science (EXAS - Get Report) ] playbook by going direct to consumer with a clinical grade product that requires a clinician," Left said.

He says the direct-to-consumer sales strategy ensures higher sales volumes than alternative strategies.

In a phone interview with TheStreet, Left also said, "The total addressable market is for everyone on Earth." 

Left's main comparable for Invitae is indeed Exact Sciences. He outlined that Invitae "is growing twice as fast as EXAS and can be considered high science."

Therefore, "If it were to trade at the same multiple, that would put Invitae at $80 - today."

Invitae trades at an enterprise-value-to-sales multiple of 14 times, while Exact Sciences trades at twice that multiple.

But Invitae "can also become a 50%-gross-margin business due to the acquired technology and IP while lowering COGS to levels unseen in the industry," Left said.

Still, the gross margin at Exact Sciences, Madison, Wis., is expected to reach 76% by 2021, according to FactSet. 

A few weeks ago, positive commentary from Left moved Invitae shares up 7%. 

The one risk Left sees is "market sentiment," he told TheStreet.

"If the market sours on companies that lose money," the stock may not perform to his expectations. 

For the first quarter, Invitae narrowed its net loss to 47 cents a share from 66 cents. Shares outstanding rose 46% to 79.4 million. Revenue climbed 47% to $40.6 million.