PTC Therapeutics' (PTCT) Phenylketonuria physician survey yielded mixed results for sustained Sephience launch momentum, pointing to room for additional switching from Kuvan and a steady number of untreated PKU patients, RBC Capital Markets said Monday.

Meanwhile, some doctors expect Sephience's market share in three years to be "only modestly higher than today," well below consensus expectations for the product's growth, RBC said.

The brokerage expects in-line Q2 Sephience sales of $144 million given the launch momentum, but still sees higher potential for medium-term growth deceleration than Street expectations, according to the note.

RBC kept a sector perform rating on PTC Therapeutics with a price target of $85.

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