The Big Bang Theory is already set to end its run with its current 12th season. But could CBS lose both of Chuck Lorre’s long-running comedy series?

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The Lorre-executive produced Mom is in the midst of its sixth season, the last under stars Anna Faris and Allison Jamey’s original contracts.

I hear CBS would like to get another season of the praised sitcom, which is currently the network’s #3 comedy series among total viewers and adults 18-49 behind Lorre’s Big Bang and Young Sheldon, and could move to #2 after the end of Big Bang. It finished last season as the third most watched comedy in broadcast TV and as a Top 5 comedy in 18-49 and 25-54.

In preparation for a possible renewal, I hear producing studio Warner Bros. TV over the past month or so reached out to Faris and Janney about new deals. I hear the two actresses went in together and there has been some initial back and forth but the two sides are still very far apart on the money as Faris and Janney are seeking significant salary increases. All parties involved declined comment.

Faris and Janney are believed to be currently making under $200,000 an episode each. That is well below the $1 million an episode the five main stars of Big Bang were getting by Season 8. Big Bang is one of those singular giant hits that are in a league of their own. But Mom has been a strong performer for CBS and WBTV. In addition to its solid ratings on the network, Mom, which crossed the 100 episode mark last season, has been sold to TV Land and CMT in off-network syndication and to the Tribune stations in broadcast syndication.

Mom also is a rare sitcom that tackles important issues. Created by Chuck Lorre, Eddie Gorodetsky and Gemma Baker, Mom stars Faris and Janney as daughter/mother duo Christy and Bonnie Plunkett, who, after having been estranged for years while both were struggling with addiction, attempt to pull their lives and their relationship together by trying to stay sober.

“Mom has been a lynchpin comedy for us over the last several years,” CBS Entertainment president Kelly Kahl said at the time of Mom‘s Season 6 renewal earlier this year. “It’s a fearless series that tackles provocative social issues with laughter and grace, and a large, loyal audience has followed. With gifted talents like Anna and Allison leading a great ensemble cast, and a production team headed by Chuck Lorre, Eddie Gorodetsky, Nick Bakay and Gemma Baker, this series just keeps getting better.”

The Mom negotiation may get extra scrutiny in light of the ongoing drive for gender equality as it is a rare comedy with female leads. Both Faris and Janney are accomplished. Mom was the first TV series for Faris who had built a formidable feature career before she was approached to do the comedy, bought by CBS with her on board. Meanwhile, Janney, one of the most heralded TV actresses working today who has won seven Emmys, including two for Mom, is coming off an Oscar win for I, Tonya earlier this year.