Asco 2021 – Merus’s slight improvement might not win over investors

The group still has its eye on accelerated approval, though genetic testing casts a long shadow.

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Merus was one of the big losers of the Asco abstract drop last month. The group’s stock fell 16% despite promising data in pancreatic cancer with its targeted therapy zenocutuzumab, as investors were left unimpressed by the response rate across other cancer types.

At Asco today Merus presented updated – and slightly better – data. Whether this will be enough to satisfy shareholders is an open question, but it is something the group’s chief executive, Bill Lundberg, is not worrying about too much. “If I were good at finance I’d be in finance,” he told Evaluate Vantage. “I like making medicines.”

He maintained that zenocutuzumab, a bispecific targeting Her2 and Her3, could be a “real medicine” for all patients with NRG1 fusions, the niche that Merus is targeting. However, he admitted that identifying pancreatic cancer patients with this genetic mutation has been tough, as the lack of approved targeted drugs for the disease means that molecular testing is not widespread.

Indeed, the company has been paying for testing for pancreatic cancer patients who might be eligible for its programmes. It might be that pancreatic cancer, where Merus is seeing activity, is hard to crack because no genetic testing is currently in place, while in more commonly tested tumours Merus's responses are insufficiently impressive.

Small population Enrgy

Merus estimates that 0.5-1.5% of pancreatic cancer patients have NRG1 fusions, and that the rate is 0.3-3% in lung cancer. These were the two main cancer types included in the phase 1/2 Enrgy study that made up the bulk of today’s Asco presentation; the remaining patients came from an early-access programme.

Merus's improving Asco data
  Asco (abstract) Asco (presentation)
Cutoff Jan 12, 2021 Apr 13, 2021 
ORR – overall 27% (9/33) 31% (14/45)*
ORR – pancreatic cancer 40% (4/10) 42% (5/12)
ORR – NSCLC Not given 29% (7/24)*
ORR – other solid tumours Not given 22% (2/9)
*Includes one PR confirmed after cutoff date. Source: Asco & company releases.

The response rate in pancreatic cancer has improved slightly since the last data cut, but more important for sentiment will be zeno’s showing in NSCLC, a larger market.

Mr Lundberg insisted that the 29% ORR in NSCLC, which included a partial response confirmed after the cutoff date, was “a really meaningful result in patients with previously treated lung cancer”. Patients had received a median of two previous therapies, which typically included a chemo/checkpoint inhibitor combo first line.

Gauging whether this was in fact a decent response is tricky, as there are currently no benchmarks in the relatively new post-checkpoint inhibitor setting.

The other cancer types treated with zeno included breast, colorectal, renal cell and endometrial, cholangiocarcinoma, neuro-endocrine carcinoma and soft tissue sarcoma.

Accelerated approval?

Merus is continuing enrolment into Enrgy, but Mr Lundberg would not say exactly how many patients the group was targeting in total.

When asked if the trial could be used as the basis for accelerated approval, he replied that Merus “does not provide details about any conversations with regulatory authorities”. But he hinted that this might be possible, saying there were precedents of other oncology drugs getting an accelerated nod off the back of studies that were “similar in size, scope and approach to Enrgy”.

If zeno does get a broad thumbs-up, NRG1 fusion testing in NSCLC might be more readily adopted than in pancreatic cancer: the wide range of targeted therapies already approved for NSCLC means that many patients already get their cancer's molecular profile tested.

“Most of these tests will pick up on NRG1 fusions,” Mr Lundberg said.

There is not much competition in the NRG1 fusion space – Elevation Oncology and Hummingbird Bioscience, which is set to start clinical trials soon, are Merus's only real rivals. According to Mr Lundberg, these groups’ anti-Her3 antibodies are less potent than his company’s dual approach.

Now Merus just has to convince the FDA.

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