Company watchers remained upbeat as analysts during a conference call Friday pressed Immunomedics Inc. for details about the complete response letter (CRL) regarding the BLA related to antibody-drug conjugate (ADC) sacituzumab govitecan for metastatic triple-negative breast cancer (TNBC).

But those won't be known for a while. CEO Michael Pehl said the CRL brought up "questions that we felt we had handled already," and in any case are "fully addressable," relating entirely to chemistry, manufacturing and control (CMC) matters and none are related to sites, data or partnerships. Questioners asked several different ways what exactly the agency wants; Pehl replied that the letter had only arrived 12 hours earlier.

The drug is meant for patients who have been given at least two prior therapies and, if approved, would be the first and only ADC approved in the indication. "Give us the time to digest and go back to the agency," Pehl said. "This is not a clinical discussion, this is not a safety discussion, [and] this is not a tox discussion." Asked whether the firm will keep Wall Street informed at each step, he promised "a very full update once we have the interaction, because that allows us to really determine the timeline. We've always tried to be transparent."

Robert Iannone, chief medical officer, said officials will meet with the FDA soon. "You could be sure that we're going to be pushing to have this timeline be as short as possible," he said. "We realize how important this is to patients." He said the Morris Plains, N.J.-based company lacks "full clarity" on whether the government shutdown will affect scheduling of talks, but regulators haven't warned to that effect. "We're not being cagey here," he said, but will wait until the FDA meeting before going into the fine points of the CRL.

The question from Morgan Stanley's Matthew Harrison was especially pointed. "Look, given that you're not willing to address the specific issues, can you talk to us at all about the scope of the issues? Are they very different from each other? Are they very similar? Is it a handful of issues? Is it tens of issues?"

Iannone said that "for obvious reasons we wouldn't get into specifics" of the CRL. "Quite literally, our next step is to get back to the FDA and say, 'Where is the gap and how do we solve that quickly?'"

Harrison cited other companies that have had a similar disagreement with the FDA, and wanted to know if Immunomedics has "any sense of how wide that gap is."

"We haven't said that there's a major gap, and that's quite intentional," Iannone replied.

Also known as IMMU-132, the compound last month was the subject of "negative commentary related to an FDA inspection of the manufacturing site for [its] hRS7 antibody component," Jefferies analyst Chris Howerton pointed out in a report. He called the stock's weakness from [the] CMC inspection overdone," and said at the time that any problems likely would be handled by the PDUFA date, which was Friday.

Apparently not. In a new report Friday, Howerton predicted the approval will be held up about 12 months. "As we believe a re-inspection will be required, we expect the resubmission would be a class II, which typically takes about six months to review," he wrote. "With that said, as IMMU-132 has breakthrough status, the company is optimistic about the upcoming FDA interactions to be flexible and supportive for approval. We would also note that the secondary supplier of the antibody component of IMMU-132 has completed tech transfer, is performing engineering runs, and is expected to be fully online in 2020." The supplier is Samsung Biologics Co. Ltd., of Incheon, South Korea.

Cowen analyst Phil Nadeau in a report called his firm's mood "disappointed that sacituzumab was not approved for metastatic TNBC on today's PDUFA date, particularly given the clinical data and major unmet need in the indication. Nonetheless, we look on this as a delay, and remain confident that sacituzumab will eventually become a standard therapy" in the disease.

At the San Antonio Breast Cancer Symposium in early December, Immunomedics provided an update on the TNBC candidate, saying the firm had submitted updated phase II data to support an ongoing FDA priority review while also reaching an accord with the agency on the design of a registration-enabling trial for the drug in HR-positive/HER2-negative metastatic breast cancer. Jefferies' Howerton called the latest word "incrementally positive," adding five months of follow-up to the TNBC study. The new data painted a picture that he said was "slightly" better, with an objective response rate of 34 percent based on a blinded independent central review and a duration of response hitting a median of 9.1 months. (See BioWorld, Dec. 7, 2018.)

The upcoming global phase III trial will test sacituzumab govitecan in about 400 patients with HR-positive/HER2-negative mBC who have failed prior hormonal and CDK 4/6 inhibitor therapies, as well as at least two prior chemotherapies. The primary endpoint of the open-label study will be progression-free survival, with additional secondary endpoints including overall survival, clinical benefit rate, health-related quality of life, and safety and tolerability. Eligible patients will be randomized 1-to-1 to receive either IMMU-132 or physicians' choice of chemotherapy and will be treated until tumor progression, unacceptable toxicity, study withdrawal or death.

Shares of Immunomedics (NASDAQ:IMMU) closed Friday at $13.31, down $4.78 or 26.4 percent.

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