Neon shines, but larger trials needed to illuminate full effect

Neon's cancer vaccine makes a decent early showing, but overall survival remain a crucial measure.

If Neon Therapeutics was to receive a report card for the results of its phase Ib trial for novel neoantigen cancer vaccine, NEO-PV-1, the comment might read something like: “Good start, needs to keep up the hard work”.

The crucial point for Neon, which today reported results of the 82-patient study in patients with advanced or metastatic melanoma, NSCLC and bladder cancer, was the validation of its technology platform. Until now many in the market had been wary of attributing much, if any, value to the novel immunotherapy approach.

Neoantigens are proteins that occur only in cancer cells, owing to genetic mutations, making them ideal targets for cancer treatments. Neon’s vaccine NEO-PV-1 directs the immune system towards these neoantigens, and today it looked as if the approach might have legs.

Today's results were from a trial that tested the project in combination with Opdivo, and improvements in progression-free survival were seen across all three tumour types. In 27 patients with metastatic NSCLC and 21 patients with bladder cancer, PFS reached 5.6 months in both groups. More impressively, in 34 patients with metastatic melanoma patients, median PFS had not been reached after 13.4-months of follow up. 

Hold your horses

Given that these are very sick patients who at the start of the trial had been through at least one and sometimes three previous lines of therapy, the results look impressive, particularly in melanoma.

But it should be remembered that this remains a small, single-arm study, while the inclusion of Opdivo means that it is hard to determine the exact benefits of NEO-PV-1. Moreover, no figure for overall survival, the industry gold standard measure, was reported, and questions were also asked about the overall response rate in some of the study arms – particularly among NSCLC patients, where there were a relatively high number of dropouts.

Investors, while not exactly piling in, saw enough in the results to start placing bets on the treatment approach, with Neon shares moving up 5% in early market trading.

Moving on

The results do at least give Neon the confidence to move into phase II. Today the group said it would be initiating a randomised phase II clinical trial of NEO-PV-1 in combination with a checkpoint inhibitor trial in metastatic melanoma.

This larger trial should answer some of the questions about the vaccine’s ongoing efficacy and duration of effect, and also explore some of the theories the group has about a potential cascading immune response triggered by the vaccine. This could get round the ever-present problem of tumour resistance.

Neon is also sensibly hedging its bets on the checkpoint inhibitor front with a study looking at NEO-PV-1 in combination with Keytruda.

Given pharma’s hunger for novel cancer targets, Neon is likely to stay in the spotlight for some time to come. Though its relatively small market cap of $129m suggests that many remain to be convinced about the company's technology.

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