Mirati Therapeutics' pain continued Thursday amid a series of analyst downgrades after MRTX stock lost about half of its value in three days.
Earlier this week, Mirati said 49% of patients with advanced lung cancer responded to a regimen using its drug, adagrasib, and Merck's immuno-oncology drug Keytruda. But that wasn't much better than the 48% overall response rate for Keytruda plus chemotherapy, a standard treatment.
"In our view, these results have yet to conclusively demonstrate a benefit of (immuno-oncology) plus chemo," SVB Securities analyst Andrew Berens said in a note to clients.
Berens says his outperform rating on MRTX stock is under review. According to reports, analysts with Citi, BMO Capital Markets and JP Morgan all downgraded shares.
MRTX Stock: Steep Dives This Week
On the stock market today, MRTX stock tumbled 11.6% to 43.85. That followed a nearly 23% dive on Tuesday and a loss of almost 31% Wednesday. For the week, shares have lost more than 54%.
Mirati's adagrasib blocks a protein often tied to cancer known as KRAS. Specifically, it focuses on a mutation known as G12C. The Food and Drug Administration is soon to make a decision on whether to approve adagrasib as a solo treatment for patients with non-small cell lung cancer who worsened on at least one previous treatment. Amgen is the only company with a product, so far, for these patients.
The data released Tuesday, though, is for the adagrasib and Keytruda combination in patients with previously untreated non-small cell lung cancer.
Mirati argued patients with the G12C mutation don't respond as well as other patients to Keytruda plus chemotherapy, Berens said. For this reason, the company believes it should have a lower bar to show the effectiveness of its regimen. It also argued there's a high unmet need among these patients.
Chief Executive David Meek expects the responses to deepen with time. Mirati is planning to convert its current study into a pivotal study. This means the data from the study could eventually be submitted to the FDA for review ahead of a potential approval.
"Across both our monotherapy and combination experience, we've seen approximately 25% of patients respond after at least three months of therapy," he said in an email to Investor's Business Daily. "We continue to be confident in our plan for adagrasib in (previously untreated) KRAS G12C-mutated non-small cell lung cancer and look forward to executing on our Phase 3 program."
Phase 3 Study planned
But MRTX stock investors didn't buy it.
"Ultimately, the company will have to succeed in demonstrating superiority of adagrasib over (immuno-oncology) plus chemo in a single clinical trial, and we do not believe investors found these cross-trial analyses as compelling," Berens said.
CEO Meek emphasized the early data demonstrate strong safety and tolerability for adagrasib plus Keytruda. Amgen is still studying its rival drug, Lumakras, in combination with Keytruda. Early on, the company noted some liver concerns.
Meanwhile, MRTX stock continued its major downfall Thursday. Shares have already abandoned a cup base with a buy point at 95.79 that began forming in August, according to MarketSmith.com.
MRTX stock also has dropped well below key moving averages.
Follow Allison Gatlin on Twitter at @IBD_AGatlin.
