gamma interferon and its methods of preparation , including synthesis in recombinant cell culture , are well known ( ep 77 , 670a and 146 , 354a ). included within the scope of gamma - interferon are gamma interferon from recombinant or native sources as well as gamma - interferon variants , such as amino acid sequence variants , e . g ., cys - tyr - cys or descys - tyr - cys amino terminal species . also included are other insertions , substitutions or deletions of one or more amino acid residues , glycosylation variants , unglycosylated gamma - interferons , organic and inorganic salts and covalently modified derivatives of gamma - interferon . the effective amount of gamma - interferon to be formulated in the liquid composition is selected based on several variables , including the disease to be treated and therapeutic regimen . generally the gamma - interferon has an activity in a standard bioassay in the range of 1 × 10 6 to 2 × 10 7 u / mg protein or more . examples of the polyhydric sugar alcohols to be used as the stabilizer in the present invention to insure isotonicity of the composition are those of trihydric or higher , such as glycerin , erythritol , arabitol , xylitol , sorbitol and mannitol . these polyhydric sugar alcohols can be used alone or in a combination thereof . in view of stabilization of interferon , the sugar alcohol is formulated in an amount of 1 % to 25 % by weight and preferably , 2 % to 5 % by weight taking into account the amounts of the other ingredients . the organic acid buffers to be used in the present invention to maintain the ph in the range of about 4 . 0 to 6 . 0 and preferably from 4 . 5 to 5 . 5 can be conventional buffers of organic acids and salts thereof such as citrate buffers ( e . g ., monosodium citrate - disodium citrate mixture , citric acid - trisodium citrate mixture , citric acid - monosodium citrate mixture , etc . ), succinate buffers ( e . g ., succinic acid - monosodium succinate mixture , succinic acid - sodium hydroxide mixture , succinic acid - disodium succinate mixture , etc . ), tartrate buffers ( e . g ., tartaric acid - sodium tartrate mixture , tartaric acid - potassium tartrate mixture , tartaric acid - sodium hydroxide mixture , etc . ), fumarate buffers ( e . g ., fumaric acid - monosodium fumarate mixture , fumaric acid - disodium fumarate mixture , monosodium fumarate - disodium fumarate mixture , etc . ), gluconate buffers ( e . g ., gluconic acid - sodium gluconate mixture , gluconic acid - sodium hydroxide mixture , gluconic acid - potassium gluconate mixture , etc . ), oxalate buffers ( e . g ., oxalic acid - sodium oxalate mixture , oxalic acid - sodium hydroxide mixture , oxalic acid - potassium oxalate mixture , etc . ), lactate buffers ( e . g ., lactic acid - sodium lactate mixture , lactic acid - sodium hydroxide mixture , lactic acid - potassium lactate mixture , etc .) and acetate buffers ( e . g ., acetic acid - sodium acetate mixture , acetic acid - sodium hydroxide mixture , etc .). it is noteworthy that inorganic acid buffers such as phosphate buffers which have been used traditionally do not maintain the ph of the liquid formulation at the desired ph . examples of the non - ionic detergents include such surfactants as pluronics , for example , polysorbate 80 and polysorbate 20 . the non - ionic detergent is present in a range of 0 . 05 mg / ml with a preferred range of about 0 . 07 to 0 . 2 mg / ml and a most preferred amount of about 0 . 1 mg / ml . the liquid formulation of this invention at a ph of 4 to 6 , preferably 4 . 5 to 5 . 5 and most preferably at ph 5 , demonstrates limited aggregation upon warming . rather than being labile the liquid formulation of this invention is stable for prolonged periods . the formulation of this invention may be stored in a liquid state at various temperatures . a preferred storage temperature is in the range of - 20 ° c . to 30 ° c . with a most preferred temperature storage range of about between 2 ° and 8 ° c . all of the components are important for maintenance of biological activity and physical stability . furthermore , the liquid formulation of this invention will retain biological activity and physical stability without freezing . this avoids potential aggregation upon thawing . the following examples illustrate the present invention , but are not to be construed to limit the scope of the invention . human recombinant gamma - interferon ( 20 × 10 6 u / mg ) was formulated by adding either 1 . 0 or 0 . 2 mg / ml to : succinic acid ( 0 . 27 mg / ml ); disodium succinate ( 0 . 73 mg / ml ); mannitol ( 40 mg / ml ); polysorbate 20 ( 0 . 1 mg / ml ); and a sufficient quantity of water for injection ( usp ). this liquid formulation was found to exhibit a long shelf life when maintained at a storage temperature of about between 2 ° and 8 ° c . in a liquid state . the succinate buffer maintained the liquid formulation at ph 5 . 0 . the non - ionic detergent prevented aggregation during shipping and handling . the sugar rendered the formulation isotonic without the need for the addition of salts , which have been shown to cause aggregation of gamma - interferon . and further , the sugar appears to stabilize the pharmaceutical composition of this invention ( compare the succinate / mannitol lyophilized formulation to the hsa / phosphate lyophilized formulation ). the liquid formulation of this invention using 0 . 2 mg / ml of non - lyophilized gamma - interferon was compared to two other lyophilized formulations of gamma - interferon . as seen in table i below , the loss of bioactivity reflected in the rate constants was ten - fold greater for the succinate / mannitol lyophilized formulation and five - fold greater for hsa / phosphate lyophilized formulation than the liquid formulation of this invention . these changes in the bioactivity are reflected in the rate constant which is the slope of the line resulting from a plot of the natural logarithm of the loss of bioactivity of the gamma - interferon formulation versus time . bioactivity was measured using a viral protection assay known to the ordinarily skilled artisan . the lyophilized compositions were stored in lyophilized form and were reconstituted at various times to determine the bioactivity remaining in the lyophilized preparation . the shelf life of the liquid formulation of this invention was considerably greater than that of the lyophilized formulations . the greater shelf life of the liquid formulation relative to the lyophilized formulation listed in table 1 shows that the liquid formulation of this invention retains biological activity ten times longer than the lyophilized compositions . table 1______________________________________comparative stability of gamma - interferonformulated at 0 . 2 mg / ml . sup . 1 rate relative study constant shelf lifeformulation ( months ) × 10 - 3 ( days ). sup . 2______________________________________succinate / 6 2 . 854 1mannitollyophilizedsuccinate / 4 0 . 205 10mannitolliquidhsa / 3 1 . 038 5phosphatelyophilized . sup . 3______________________________________ . sup . 1 based on real time 5 ° c . data . . sup . 2 a comparison of the relative stability based on the bioactivity of the three formulations with the succinate / mannitol lyophilized compositio being arbitrarily set at 1 . . sup . 3 this formulation was prepared by mixing 0 . 20 mg lyophilized gammainterferon , 10 mg hsa , 5 mm sodium phosphate ph 7 . 0 and reconstitute with 0 . 9 % saline . a similar comparative study was carried out for the liquid formulation of this invention using 1 . 0 mg / ml of non - lyophilized human recombinant gamma - interferon . once again , as shown in table 2 , the loss of bioactivity was greater for the lyophilized formulation than for the liquid formulation of this invention . table 2 also shows that the shelf life of the liquid formulation of this invention was three times greater than that of the lyophilized formulation . table 2______________________________________comparative stability of gamma - interferonformulated at 1 . 0 mg / ml . sup . 1 study rate relative time constant shelf lifeformulation ( months ) × 10 - 3 ( days ). sup . 2______________________________________succinate / 14 0 . 485 1mannitollyophilizedsuccinate / 14 0 . 179 3mannitolliquid______________________________________ . sup . 1 based on real time 5 ° c . data . . sup . 2 a comparison of the relative stability based on the bioactivity of the two formulations with the succinate / mannitol lyophilized composition being arbitrarily set at 1 .
a liquid pharmaceutical composition comprising an effective amount of non - lyophilized gamma - interferon . the liquid pharmaceutical composition which additionally includes a buffer capable of maintaining the ph of the liquid composition within the range of 4 . 0 to 6 . 0 , a stabilizing agent and a non - ionic detergent .