* Antex Biologics Inc., of Gaithersburg, Md., and its partner, SmithKline Beecham plc, of London, began a Phase II trial of the former's Campylobacter vaccine for prevention of infections caused by the bacteria. The vaccine combines inactivated whole cells of Campylobacter with an adjuvant. The blinded, placebo-controlled trial will evaluate the vaccine's effectiveness in protecting healthy adults from the infection, which can lead to life-threatening diarrhea.

* BioChem Pharma Inc., of Laval, Quebec, changed its NASDAQ National Market symbol to BCHE.

* MedImmune Inc., of Gaithersburg, Md., adopted a shareholder rights plan to prevent unwanted takeovers of the company. MedImmune officials said the move was not in response to any specific acquisition attempt.

* Cortex Pharmaceuticals Inc., of Irvine, Calif., raised $2 million in the second tranche of a $4 million private placement of convertible preferred stock. The company said it ended fiscal 1997 on June 30 with $7.5 million, which will support operations through calendar year 1998.

* Ergo Science Corp., of Boston, began a Phase II/III study to evaluate Ergoset as a weight loss drug in 400 clinically obese patients. The company already has conducted Phase III trials showing the drug, an oral form of bromocriptine, was effective in controlling blood glucose levels in Type II diabetics. Bromocriptine is a generic dopamine agonist approved by the FDA for treatment of Parkinson's disease. In obese Type II diabetes patients, Ergoset demonstrated it could lower certain blood lipids. The company said other clinical studies and preclinical trials suggest the drug reduces body fat. If the trial in clinically obese patients proves successful, larger-scale studies will be conducted to support filing a new drug application for Ergoset to treat obesity.

* RiboGene Inc., of Hayward, Calif., signed an agreement with CSC Pharmaceuticals Inc., of Vienna, Austria, for rights to develop and market RiboGene's Emitasol in Eastern Europe and Russia. RiboGene received an undisclosed up-front payment and will receive royalties. Emitasol, intranasal metoclopramide, is used to treat vomiting and nausea associated with chemotherapy. RiboGene acquired the drug in its 1994 acquisition of Hyline Laboratories.

* Vertex Pharmaceuticals Inc., of Cambridge, Mass., said its partner, Glaxo Wellcome plc, of London, launched a second Phase III trial of the former's HIV protease inhibitor, VX-478, in combination with nucleoside reverse transcriptase inhibitors. The study will evaluate Vertex's drug in children with HIV. The first Phase III trial, begun in February 1997, is testing VX-478 in adults in combination with AZT and 3TC, two nucleoside reverse transcriptase drugs sold by Glaxo. Vertex's VX-478 was developed in collaboration with Glaxo and Kissei Pharmaceutical Co. Ltd., of Matsumoto, Japan.