Genex Corp., a Gaithersburg biotechnology company, has reported a 1985 loss of $15.9 million ($1.25 a share) on revenue of $16.2 million. That compares with a 1984 loss of $7.4 million (58 cents) on revenue of $26.4.

The company said it lost $9 million (70 cents) in the fourth quarter on revenue of $1.9 million, compared with a loss of $7.4 million (59 cents) on revenue of $1.1 million the year before.

The bigger loss and lower revenue reflect the decline of the company's sales of L-phenylalanine, an amino acid ingredient in the popular sweetener aspartame. G. D. Searle & Co., Genex's major customer for L-phenylalanine, first lowered the price it paid Genex and then discontinued its purchase contract for the ingredient.

After losing the Searle contract, Genex has offered to sell its L-phenylalanine manufacturing plant. The company said most of the increase in the 1985 net loss reflects the write-down of the plant and the estimated costs related to its disposal.

*American Management Systems Inc., a computer systems engineering and services firm, reported 1985 profits of $3.7 million ($1.48 a share), a 31 percent increase over net income of $2.8 million ($1.13) in 1985.

Revenue increased to $112.2 million last year from $97 million the year before.

The Arlington company reported fourth-quarter earnings of $1.4 million (57 cents), up 53 percent over net income of $937,000 (37 cents) in the same period in 1984. Fourth-quarter revenue rose to $31.6 million from $27.6 million the year before.

The per-share earnings for prior periods have been restated to reflect the 3-for-2 stock split effective last August.

*Iverson Technology Corp. of McLean reported 1985 earnings of $1.8 million (90 cents a share), or triple its 1984 net income of $608,250 (35 cents).

Revenue grew to $17.2 million last year from $6.2 million in 1984.

The computer system integration company reported a fourth-quarter profit of $565,573 (23 cents), a 20 percent increase over 1984 fourth-quarter net income of $470,000 (27 cents). The results reflect an increase in the number of shares outstanding. Quarterly revenue increased to $5.3 million from $3.5 million.

*B. F. Saul Real Estate Investment Trust, citing increases in interest expenses, reported a net loss of $3.7 million (68 cents a share) for the first quarter ended Dec. 31. The trust lost $1.3 million (24 cents) for the same three months in the previous year.

The major reason for the declining results was a 39 percent increase in net interest expense resulting from new financing placed on the trust's operating properties, the company said. Saul also said that the performance of its income-producing properties, particularly office and industrial property, was off in the first quarter.

*Computer Network Corp. (Comnet), which provides a range of computer services, reported a loss of $1.6 million (68 cents a share) for its third quarter after taking a number of balance sheet write-downs. In the same period a year ago, the three months ended Dec. 31, 1984, the company recorded earnings of $107,0004 cents).

The company said the writedowns included charges associated with its 1982 purchase of Data Systems Consulting Corp., inventory write-downs, and costs incurred through the company's Ford Laboratories subsidiary.

Without the write-downs and one-time charges, Comnet said it would have recorded a small operating profit during the quarter.

*Flow General Inc., a scientific firm specializing in biomedical products, said that it lost $467,000 (5 cents a share) in the three months ended Dec. 31, an improvement over the $636,000 (7 cents) it lost in the same period a year ago.

The earnings came on sales of $38.9 million in the fiscal 1986 second quarter, compared with $36.1 million in the 1985 quarter.

Flow is emerging from a spate of serious legal problems, and its president, Robert E. Wengler, said, "At this stage of our recovery, the exact numbers mean little. What matters is that losses are a small percentage of revenues -- or close to break even -- and an improvement over . . . last year."