IMGN - ImmunoGen Before The PDUFA

Summary

• ImmunoGen has a PDUFA on November 28.
• The NDA is based on data from the Soraya trial.
• The PFS data creates some doubt in investors.

ImmunoGen ( IMGN ) has a tryst with the FDA on November 28, a priority review of its BLA for mirvetuximab soravtansine backed by stellar results from the pivotal phase 3 SOROYA trial for mirve as monotherapy in high FR? expression patients with ovarian cancer.

I covered IMGN just about a year ago, when the company still didn't have data from SOROYA. At ASCO 2021, they published data from FORWARD II, which was also impressive, but did not move the stock as much. Then on November 30 last year, they published outstanding mirve data from SOROYA, and the stock immediately took off. The stock, today, is trading at almost exactly the same price where it was a year back - which begs the question, should we be buying?

The SOROYA data was as follows:

• SORAYA enrolled 106 patients with a median of three prior lines of therapy.

• The trial met the primary endpoint with confirmed objective response rate ((ORR)) of 32.4% (95% confidence interval [CI]: 23.6%, 42.2%), including five complete responses ((CRS)).

• ORR by BICR was 31.6%, including five CRs.

• The median duration of response is currently 5.9 months (95% CI: 5.6, 7.7).

• Mirvetuximab was well-tolerated, consistent with the known safety profile seen in more than 700 patients treated in the broader mirvetuximab program.

As I noted earlier, historical data in a similar patient population was a mere 12%, so mirve did produce very strong data. The trial, though, was a single arm trial, with not even placebo to compare against. There's a second study, MIRASOL, which is a randomized study of mirve monotherapy in a similar patient population, comparing mirve with chemo. Topline results were due in Q3 2022, which will be a confirmatory trial (topline data is now expected in Q1 2023). However, mirve's ocular toxicity and a single patient death has investors worried. As Evaluate says:

One problem is safety, with investors being reminded about miretuximab's ocular toxicity, and one death being deemed possibly treatment related. But the big question is over the absolute progression-free survival number, which has the potential to cause Immunogen a big headache as readout of the confirmatory Mirasol trial, due in the third quarter, approaches.

In an independent review, a PFS of 5.5 months was seen, which amounts to a 2-month increase from the assumed chemo PFS of 3.5 months. However, investigator review only saw a 4.3-month PFS, which amounts to a mere 0.8 months increase. If Mirasol does not do well on these measures, the FDA may not take that kindly.

On the positive side, mirve seems to have a better result with PARPi relapsed patients. PARPis are today standards of treatment for ovarian cancer, and Soroya saw a 38% response rate in patients who progressed after PARP inhibitor treatment.

In other news, the CADENZA study on pivekimab in blastic plasmacytoid dendritic cell neoplasm, or BPDCN, which was slated to deliver data this year, has been pushed back to 2024. CADENZA is a pivotal trial in the indication, which has 700 US patients annually.

ImmunoGen, a leader in antibody drug conjugate and especially the payload-linker technology, has a number of partnerships with big pharma, including, most recently, with Eli Lilly. The company earns a steady revenue stream from these deals.

Financials

IMGN has a market cap of $1.32bn. In Q2 2022, they generated $14.2mn in revenue. R&D expenses were $51.4mn and SG&A were $23.8mn, which makes an operating expense figure of $75.2mn. Given a cash balance of $373.9mn at the time, the company can expect a cash runway to the end of 2023 at the least.

Bottomline

IMGN has a critical PDUFA date next month, based on more or less strong data in a patient population with high unmet need. The stock price, too, is less than what it was last year. However, there are questions surrounding the trial data, which adds to the risk situation. Considering all of this together, I think a cautious pilot may be warranted now before the PDUFA.

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