Osisko has acquired 50% of a royalty on the Mina Volare claim within Regulus' AntaKori landholding that hosts about 75% of the overall project's current indicated resource of 2.6 billion pounds of copper, 2.3 million ounces of gold and 61Moz of silver, and half the inferred 2.4 billion pounds of copper, 2.2Mozf gold and 67Moz silver.

Regulus had bought the royalty rights from a private vendor and onsold them to Osisko for 75% of its purchase price under their new arrangement.

Royalties covering various claims on the AntaKori project area owned by private parties can similarly be bought by Regulus, and Osisko now has the right to buy them for 75% of Regulus' purchase price.

The cost of Osisko's acquisition of the Mina Volare royalty is included in its $12.5 million upfront payment to Regulus for the broader project option.

"Through this transaction we have been able to reduce outstanding royalties on AntaKori, thereby improving the overall value of the project, while at the same time raising a significant sum of money," said Regulus CEO John Black.

"We are now fully financed to complete our Phase II drill programme which will restart shortly."

Osisko CEO Sean Roosen said the investment gave the company a "unique opportunity to gain exposure to one of the largest and highest grade undeveloped copper-gold projects in the world, located in a premier jurisdiction, and to work with a management team with a proven track record of delivering world class projects".

If Regulus sells AntaKori and receives a royalty or stream as part of the consideration, Osisko has gained the right of first refusal on that royalty or stream, too.

Regulus will also issue Osisko 5.5 million three-year warrants with an exercise price of C$2.25 per share.

Shares in regulus Resources are trading at C$1.50, valuing the company at $153 million.