By Debbie Strickland

Due to the breakage of a cell-containing pain-control implant capsule in three trial patients, CytoTherapeutics Inc. and partner Astra AB modified the surgical procedure and tether used to implant the device, which is under development for neuropathic pain and cancer.

"We will be monitoring those patients very closely, but . . . it's virtually unnoticeable [to the patients]. No harm has come to them as a result of this," said Elizabeth Razee, spokeswoman for Lincoln, R.I.-based CytoTherapeutics.

"When you're working with a device, you're expected to continue to modify the procedure based on clinical experience," she said. "This is not a serious event. It's easily modifiable."

The three patients whose implants broke are among 17 who were enrolled in a 10-week Phase IIa trial conducted at four sites in the U.S. and Europe.

The companies are implementing the changes before enrolling additional patients in the Phase IIb cancer pain trial under way in Europe, according to Richard Rose, president and CEO, who does not expect the pause "to significantly delay the time line for completion of that trial."

The implant — currently unnamed but formerly known as CereCRIB and ACTID — contains bovine adrenal cells that secrete naturally occurring analgesics such as catecholamines and opioid peptides.

The capsule is implanted in the intrathecal space in the lumbar region via a minimally invasive surgical procedure. It is important that the capsule remain floating in the cerebrospinal fluid, because it can break if it lodges in tissues that bend and move.

Doctors have to "be sure it's in that [intrathecal] space and stays there, so the issue is anchoring the device securely," Razee said.

To solve the problem, she said, CytoTherapeutics and Astra are adding a small clip to the end of the tether to be sutured into place, "so the surgeon can be absolutely certain the tether is secured."

The companies plan to move the Phase IIb European trial forward with the modified tether, with Astra pledging its continuing support.

"Based on our expertise in the field of pain management and with this technology, we are committed to the development of CytoTherapeutics' technology," said Carl-Johan Dalsgaard, president of Astra Pain Control AB.

Astra has paid CytoTherapeutics more than half the potential $41 million in milestones and research support contained in a 1995 agreement giving the Sodertalje, Sweden, pharma giant worldwide marketing right to the implant.

CytoTherapeutics' shares (NASDAQ:CTII) closed Friday at $2.456, down $0.188. *