Redx Pharma saw its stock price plunge 61% this morning, after disclosing that it has temporarily halted patient recruitment in the Phase I/IIa trial of its lead candidate, the cancer treatment RXC004, just a month after it launched.

In a statement, Redx said it informed the U.K.’s Medicines and Healthcare products Regulatory Agency (MHRA) of the temporary halt. The company cited unspecified “clinically significant adverse events” being observed in the first patient dosed with RXC004, “that the company and our academic colleagues believe are possibly related to RXC004 on-target effects and Wnt pathway inhibition.”

“It is our current intention to propose a protocol amendment that enables dose-escalation to restart at significantly lower dose levels,” stated Andrew Saunders, MBBCh, Redx’s CMO. “This protocol amendment will be finalized with consultation with both the MHRA and principal investigators.”

Shares of Redx on the London Stock Exchange plunged 61% from yesterday’s closing price of £10.25 ($14.41) as of 10:09 a.m. ET, to £4 ($5.63) per share.

Added Redx executive chairman Iain Ross: “While we remain confident that we can address this issue, we currently estimate that that this suspension will lead to a delay of several months.

“The Board continues to believe it has sufficient resources to continue to progress RXC004 and its broader portfolio of oncology and fibrosis assets,” Ross added. Redx said last month that it expected to have initial data from the Ia segment of the trial in the second half of 2018.

“The Board continues to believe the overall risk/benefit assessment of RXC004 as an investigational drug is unchanged,” Ross said, adding that Redx intends to provide a further update “in due course.”

RXC004 is a novel, oral, potent, small-molecule Porcupine inhibitor that targets the Wnt pathway, which is implicated in a range of cancers with poor prognoses, such as pancreatic, biliary, and gastric cancers. RXC004 is in clinical development both as a monotherapy for gastric, biliary, and pancreatic cancer—and in the Investigational New Drug (IND)-enabling phase as part of a combination with an unspecified anti-programmed cell death protein 1 (PD-1) checkpoint inhibitor in melanoma.

“RXC004 has the potential to be used as a biomarker-guided, targeted therapy in hard-to-treat cancers and as a combination partner in immune-oncology treatment paradigms with immune checkpoint inhibitors,” Redx states on its website.

Last month, Redx announced the start of patient dosing in the Phase I/IIa trial (NCT03447470), a first-in-man multiarm, multipart, adaptive design study designed to assess the safety and tolerability of the drug in patients with advanced solid tumor malignancies. The company has anticipated that about 50 patients will be enrolled.

In the first part of the study, Redx has said, patients were to be assigned to a dose and followed for potential dose-limiting toxicities. Once the period was completed, the protocol dictated that the next arm of the study would be at a higher dose until a maximum tolerated dose is reached.

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