A recombinant blood growth factor, GM-CSF, has improved the odds of giving higher doses of chemotherapy to kill tumor cells, without destroying infection-fighting white blood cells as well.

A clinical trial reported in the August issue of the Journal of Clinical Oncology found that GM-CSF (granulocyte-macrophage colony-stimulating factor) markedly reduced the ravages of anti-cancer chemicals on bone-marrow, which produces neutrophils -- white blood cells that mop up invading bacteria.

The major drawback of such drugs -- notably Cytoxan, Adriamycin and dacarbazine -- is that their dosage and frequency, and hence, their anti-tumor effectiveness, must be held down, to keep a patient from dying of their major side effect, neutropenia. This wipeout of white blood cells brings on life-threatening infection.

Researchers conducting the study at the University of Texas M.D. Anderson Cancer Center gave end-stage sarcoma patients escalating doses of GM-CSF supplied by Immunex Corp. and Hoechst-Roussel. Immunex expresses the genetically engineered protein in yeast cells.

After 23 patients had received 111 rounds of GM-CSF plus the Cytoxan-Adriamycin-dacarbazine cocktail, the Houston clinicians concluded: "Our results demonstrate that GM-CSF, when administered immediately after a compressed schedule of (combination) chemotherapy, enhanced myelo (bone- marrow) protection ... and allowed dose-intensification of chemotherapy."

Fortified by these and other recent clinical findings, Immunex, which supplied its GM-CSF for the trial, plans to apply to the FDA "this year to broaden the indication label to cover neutropenia caused by chemotherapy," said the Seattle company's vice president for communications, Jason Rubin. At present, Rubin told BioWorld, GM-CSF is approved only "to accelerate bone-marrow engraftment and to prolong survival when such treatment fails."

Neupogen, the G-CSF (granulocyte colony-stimulating factor) produced by Amgen, already enjoys the chemotherapy- enhancing FDA label.

Wertheim Shroder & Co. analyst Jay B. Silverman cited the Journal of Oncology Study, along with two other trials in his reiterated recommendation of the stock on Thursday.

Immunex (NASDAQ:IMNX) closed Thursday at $35.75 per share, up $1.75.

Silverman wrote that a study published in the August issue of the Annals of Internal Medicine "bodes extremely well for the potential of (Immunex's) PIXY321, which may be highly effective as a single agent molecule in raising both neutrophils and platelets, and which also may address markets where Neupogen has been ineffective."

A study sponsored by Schering-Plough published in the July issue of the Journal of American Medicine described very low doses of GM-CSF given alone or with erythropoietin to patients with aplastic anemia. Silverman wrote that this study " will help support wider usage of GM-CSF and the likelihood of an expanded label.

Jordan U. Gutterman, who chairs the department of clinical immunology and biological therapy at M.D. Anderson, commented on the trial results, which were initially reported in May 1991 to the American Society of Clinical Oncology in Houston. "Now that the article has finally been published, it is my perspective that it will have an influence among practising, as well as research, oncologists." Gutterman added, "All sorts of other studies are going on -- G-CSF, GM-CSF and IL-3-- trying the effect of these blood growth factors administered before as well as after cycles of chemotherapy. "

-- David N. Leff Science Editor

(c) 1997 American Health Consultants. All rights reserved.