EXCLUSIVE: There will be no wedding bliss chapter for Bill and Virginia. I’ve learned that Showtime has opted not to pick up a fifth season of Masters Of Sex starring Michael Sheen and Lizzy Caplan as real-life pioneers of human sexuality William Masters and Virginia Johnson. The news comes two weeks after Season 4 of the period drama ended its run on the network. UPDATE: Showtime confirmed the end of the series in a statement: “Masters of Sex was a beautifully written and acted exploration of America’s changing sexual mores. We are incredibly proud to have shared the story of Masters and Johnson for four critically-acclaimed seasons. The series will remain available across our platforms where new viewers can discover it for years to come.”

Season 4 began with the year 1968 and chronicled the “swinging ‘70s” during which time the characters took on new partners both professionally, personally and sexually. The season — and now series — finale on November 10 saw Masters and Johnson working to save the practice from disintegrating in the face of insurrection within the clinic. As everyone in their lives was either moving or falling away, Bill and Virginia found solace in one another and got married. With Bill and Virginia finally tying the knot in the Season 4 finale, I hear Showtime brass felt that was a fitting conclusion to the duo’s complicated story, and decided not to go forward with another season.

Masters Of Sex had been a prestige but modest ratings performer for Showtime. Season 4 averaged less than 800,000 in Live+3 while its lead-in, first Ray Donovan and then Shameless, both drew more than 2 million (L+3) each week. Across multiple platforms, Masters of Sex Season Four is averaging 2.16 million viewers.

Masters Of Sex was developed by Michelle Ashford loosely based on Thomas Maier’s biography of the same name. Ashford executive produced with Sarah Timberman, Carl Beverly, Amy Lippman and Judith Verno for Timberman/Beverly, Sony Pictures TV and Showtime. The series has earned a number of Emmy nominations for its first three seasons, winning in the guest actress in a drama series category for Allison Janney’s role as sexually unfulfilled housewife Margaret Scully.