* Sheds ~$19 bln in market cap
* Will not seek accelerated approval for Rova-T
* Drug key part of effort to shore up cancer portfolio - analyst
* Trials testing in earlier stages of cancer to continue -AbbVie (Adds analyst comment, updates shares)
By Tamara Mathias
March 22 (Reuters) - AbbVie Inc's experimental lung cancer drug data was not effective enough to seek a faster approval, in a setback to the company's efforts to build its cancer drug pipeline and cut dependence on its blockbuster Humira.
The company's shares were down 10.8 percent at $100.29 in early trading, shedding about $19 billion in market value.
AbbVie has been building a portfolio of oncology drugs to counter competitive threats to its rheumatoid arthritis treatment, Humira, which accounts for about two-thirds of its overall sales.
The company said on Thursday it would not seek accelerated approval for the drug, Rova-T, after consulting with the U.S. Food and Drug Administration based on "magnitude of effect across multiple parameters".
"You've got okay response rate, no evidence that there are long-term survivors and then you have a pretty onerous side effect burden," Leerink Partners analyst Geoffrey Porges told Reuters.
The mid-stage study tested Rova-T as a treatment for small cell lung cancer patients who failed to respond to at least two prior regimens.
Rova-T, which AbbVie acquired with its $5.8 billion purchase of Stemcentrx in 2016, is expected to generate sales of $1.2 billion in 2023, according to Thomson Reuters estimates.
"(AbbVie) needs something that is the cornerstone of the oncology franchise that they own and Rova-T was meant to be that," Porges said. "And now that cornerstone is cracked you wonder if they don't have to go out and find something else."
Late-stage trials testing the drug as a treatment for patients who have either failed to respond to initial treatment or are newly diagnosed will continue, the company said.
Rova-T is a toxic chemical that is loaded onto an antibody to target a protein called DLL3 found in more than 80 percent of patients with the cancer.
The FDA's accelerated approval program is meant for drugs that treat serious conditions based on a marker that is expected to lead to a clinical benefit.
Guggenheim Securities analyst Tony Butler said AbbVie will likely have to run a bigger trial that will cost more and will need to have a control arm.
"They wanted to do this with a relatively small number of patients and not have to run a control or a big study. That strategy is now thrown out." (Reporting by Tamara Mathias and Ankur Banerjee in Bengaluru; Editing by Anil D'Silva)