WO1999040106A2

WO1999040106A2 - Use of angiotensin analogues for promoting erythropoiesis

Info

Publication number: WO1999040106A2
Application number: PCT/US1999/002648
Authority: WO
Inventors: Kathleen E. Rodgers; Gere Dizerega
Original assignee: University of Southern California USC
Current assignee: University of Southern California USC
Priority date: 1998-02-09
Filing date: 1999-02-08
Publication date: 1999-08-12
Anticipated expiration: 2000-08-09
Also published as: WO1999040106A3; AU2591699A; US7745411B2; JP2002509077A; US20090062210A1; US6239109B1; EP1053004A2; CA2319701A1; CA2319701C; US7288522B1

Abstract

The present invention provides methods, compounds, pharmaceutical compositions, and kits for the augmentation of erythropoiesis by potentiating erythropoietin-induced differentiation with angiotensinogen, angiotensin I (AI), AI analogues, AI fragments and analogues thereof, angiotensin II analogues, AII fragments or analogues thereof or AII AT2 type 2 receptor agonists as a therapeutic adjunct. The method is useful for the treatment of congenital or acquired aplastic or hypoplastic anemia associated with chronic renal failure, end-stage renal disease, renal transplantation, cancer, AIDS, chemotherapy, radiotherapy, bone marrow transplantation and chronic diseases.

Description

METHOD OF PROMOTING ERYTHROPOIESIS

Cross Reference

This application is a continuation-in-part of U.S. Provisional Application Serial No. 60/074,106 filed February 9, 1998 and a continuation of U.S. Provisional Application Serial No. 60/111,535 filed December 9, 1998.

Field of the Invention

The present invention relates to compounds, methods, compositions, and kits for the stimulation of erythropoiesis. More specifically, the present invention relates to methods, compositions, and kits that employ effective amounts of angiotensinogen, angiotensin I (Al), Al analogues, Al fragments and analogues thereof, angiotensin II analogues, All fragments or analogues thereof or All AT type 2 receptor agonists for stimulating erythropoiesis.

Background of the Invention

Maintenance of an adequate supply of oxygen to the body tissues is vital to survival. In the United States alone, several million people suffer from anemia secondary to renal failure, chronic inflammatory disease and malignancies (U.S. Patent No. 4,987,121, hereby incorporated by reference in its entirety). Since to a large degree the oxygen-carrying capacity of blood is governed by the concentration of erythrocytes in the blood, the appropriate regulation of erythropoiesis is also crucial. The early studies of Reissmann (Reissmann, K. R., Blood 5:372-80 (1950)) and Erslev (Erslev, A., Blood 8:349-57 (1953)) clearly demonstrated the hypoxia- induced stimulation of erythropoietin secretion. When erythropoietin is secreted from the erythropoietin-producing cells in response to hypoxia, it travels through the blood to its target organ, the hematopoietic tissues. In humans, the principal hematopoietic tissue is within the liver before birth, and in the bone marrow after birth. (Id.) There, erythropoietin binds specifically to its receptor on the erythroid progenitor cells called burst forming unit-erythroid (BFU-E) and colony-forming unit-erythroid (CFU-E) and stimulates these cells to proliferate and differentiate (Spivak, J. L., Int. J. Cell Cloning 4:139-66 (1986)). BFU-E are the earliest erythroid progenitors and constitute 0.01%, approximately, of the nucleated bone marrow cells. CFU-E are derived from BFU-E, account for about 0.1% of marrow cells, and are much more responsive to erythropoietin than are BFU-E (Spivak, J. L., supra); Sawada, K., et al., J. Clin. Invest. 80:357-66 (1987)). The low erythropoietin levels always present appear sufficient for a basal erythropoiesis rate. Relatively small losses of blood do not appear to stimulate increased erythropoietin production (Kickler, T. S., et al., J. Am. Med. Assoc. 260:65- 7 (1988)). It is only after a major blood loss that there is an increased production of erythropoietin and rate of erythropoiesis. It has been well-established that the majority of patients with renal insufficiency and anemia have serum erythropoietin levels well below what would be expected for the degree of anemia (Caro, J., et al., J. Lab. Clin. Med. 93:449-58 (1979); Radtke, H. W., et al., Blood 54:877-84 (1979); Chandra, M., et al., J. Pediatr. 113:1015-21 (1988)), although they can still respond to hypoxia with an increase in serum erythropoietin levels (Radtke, H. W., et al, Blood 54:877-84 (1979); Chandra, M., et al., J Pediatr 113:1015-21 (1988)). However, this markedly blunted erythropoietin response substantially contributes to the pathogenesis of the anemia (Eschbach, j. W., et al., Am J Kid Dis 11:203-9 (1988)). As a result, patients suffering from chronic renal failure and end-stage renal disease, or those undergoing renal transplantation, develop severe anemia and require regular blood transfusions (Royet, U.S. Patent No. 5,482,924).

The use of recombinant human erythropoietin has facilitated treatment of these patients. However, recombinant erythropoietin treatment is extremely costly, and methods that augment the effect of erythropoiesis will permit the use of smaller doses of erythropoietin, and thus will decrease treatment costs. Additionally, increasing the rate of erythropoiesis would significantly improve clinical benefits for the treatment of congenital or acquired aplastic or hypoplastic anemia associated with chronic renal failure, end-stage renal disease, renal transplantation, cancer, AIDS, chemotherapy, radiotherapy, bone marrow transplantation and chronic diseases.

Summary of the Invention

In one aspect, the present invention provides compounds and methods for the augmentation of erythropoiesis by potentiating erythropoietin-induced differentiation with angiotensinogen, angiotensin I (Al), Al analogues, Al fragments and analogues thereof, angiotensin II analogues, All fragments or analogues thereof or All AT type

2 receptor agonists as a therapeutic adjunct.

In another aspect, the present invention provides pharmaceutical compositions comprising angiotensinogen, angiotensin I (Al), Al analogues, Al fragments and analogues thereof, angiotensin II analogues, All fragments or analogues thereof or

All AT₂ type 2 receptor agonists together with erythropoietin and a pharmaceutically acceptable carrier.

In a further aspect, the present invention provides kits for promoting erythropoiesis, wherein the kits comprise an effective amount of angiotensinogen, Al,

Al analogues, Al fragments and analogues thereof, All analogues, All fragments or analogues thereof or All AT₂ type 2 receptor agonists, and instructions for using the amount effective of active agent as a therapeutic adjunct to erythropoietin treatment. In another aspect, the invention provides improved cell culture medium for promoting erythropoiesis, comprising adding an effective amount of the active agents of the invention to promote erythropoiesis.

The methods and kits of the present invention are clinically useful as a therapeutic adjunct for increasing red blood cell production in treating congenital or acquired aplastic or hypoplastic anemia.

Brief Description of the Figures

Figure 1 is a graph showing the effect of 1GD on formation of human burst- forming units-erythroid.

Figure 2 is a graph showing the effect of 24B on formation of human burst- forming units-erythroid.

Figure 3 is a graph showing the effect of 2GD on formation of human burst- forming units-erythroid.

Figure 4 is a graph showing the effect of 5GD on formation of human burst- forming units-erythroid. Figure 5 is a graph showing the effect of AII(l-7) on formation of human burst- forming units-erythroid.

Figure 6 is a graph showing the effect of All on formation of human burst- forming units-erythroid.

Detailed Description of the Preferred Embodiments

All cited patents, patent applications and references are hereby incorporated by reference in their entirety.

As defined herein, the term "erythropoiesis" refers to red blood cell production.

As defined herein, "augmentation of erythropoiesis" may occur either by direct stimulation of erythroid production, by increasing erythropoietin production, or by any other mechanism.

Unless otherwise indicated, the term "active agents" as used herein refers to the group of compounds comprising angiotensinogen, angiotensin I (Al), Al analogues, Al fragments and analogues thereof, angiotensin II analogues, All fragments or analogues thereof and All AT type 2 receptor agonists.

The biological formation of angiotensin is initiated by the action of renin on the plasma substrate angiotensinogen (Circulation Research 60:786-790 (1987); Clouston et al., Genomics 2:240-248 (1988); Kageyama et al., Biochemistry 23:3603- 3609; Ohkubo et al, Proc. Natl. Acad. Sci. 80:2196-2200 (1983); all references hereby incorporated in their entirety). The substance so formed is a decapeptide called angiotensin I (Al) which is converted to All by the converting enzyme angiotensinase which removes the C-terminal His-Leu residues from Al (Asp-Arg- Val-Tyr-Ile-His-Pro-Phe-His-Leu [SEQ ID NO:37]). All is a known pressor agent and is commercially available.

Angiotensin-converting enzyme (ACE) inhibitors have been observed to exacerbate anemia in patients with chronic renal failure and end-stage renal disease (ESRD), as well as in renal transplant recipients (Cruz et al., Am. J. Kidney Diseases 28:535-540 (1996); herein incorporated by reference in its entirety). ACE inhibitors appear to induce anemia by decreasing red blood cell production (Id.) Some data exist which suggest that ACE inhibitors may reduce red blood cell production by inhibiting angiotensin-mediated erythropoietin synthesis. (Hirikata et al., Clin. NephroL 26:27-32 (1986); Gould et al., J. Lab. Clin. Med. 96:523-534 (1980); Conlon et al., Transplantation 56:217-219 (1993)). However, other studies show that ACE inhibitors do not inhibit erythropoietin synthesis, and suggest that angiotensin does not play a role in erythropoiesis. (Cruz et al., 1996; Anderson et al., Biology of the Neonate 71 :194-197 (1997); Shand et al., J. Hum. Hypertension 9:233-235 (1995); Julian et al., Kidney Int. 46:1397-1403 (1994); Gaston et al., Transplant Proc. 25:1029-1031 (1993); Islam et al., Transplant Int. 3:222-225 (1990); Rostaing et al, Transplant Proc. 26:280-281 (1994)). Thus, it is unclear whether All, or any All analogues and fragments, stimulate production of erythropoietin.

A recent study suggests that activation of the ATI receptor with angiotensin II enhances erythropoietin-stimulated human erythroid proliferation in vitro. (Mrug et al., J. Clin. Invest. 100 (9):2310-2314 (1997). Previous studies have indicated that slow infusion of angiotensin II in dogs (Fisher et al., in Annals New York Academy of Sciences, pp. 308-317: 1968) and mice (Fisher et al., J. Pharmacol, and Exper. Therapeutics 157:618-625, 1967) led to increased erythropoietin production, while injections of angiotensin II into mice and rats did not lead to such an increase. (Mann et al., P.S.E.B.M. 121:1152-1154 (1966); Bilsel et al, P.S.E.B.M. 114:475-479 (1963)). Thus, there is some evidence that angiotensin II (All) stimulates erythropoiesis in vitro, while the in vivo data is unclear. However, there is no data suggesting whether any All analogues and fragments also stimulate erythropoiesis, whether in vitro or in vivo. For example, data suggests that the All fragment AII(l-7) acts through a receptor(s) that is distinct from the ATI and AT2 receptors which modulate All activity. (Ferrario et al., J. Am. Soc. NephroL 9:1716-1722 (1998); Iyer et al., Hypertension 31:699-705 (1998); Freeman et al., Hypertension 28:104 (1996); Ambuhl et al., Brain Res. Bull. 35:289 (1994). Thus, the stimulatory effect of All through activation of the ATI receptor reported by Mrug et al. (see above) does not shed any light on the potential stimulatory effect of AII(l-7).

U.S. Patent No. 5,015,629 to DiZerega (the entire disclosure of which is hereby incorporated by reference) describes a method for increasing the rate of healing of wound tissue, comprising the application to such tissue of angiotensin II (All) in an amount which is sufficient for said increase. The application of All to wound tissue significantly increases the rate of wound healing, leading to a more rapid re-epithelialization and tissue repair. The term All refers to an octapeptide present in humans and other species having the sequence Asp-Arg-Val-Tyr-Ile-His- Pro-Phe [SEQ ID NO: 1]. The use of All analogues and fragments, AT2 agonists, as well as AIII and AIII analogues and fragments in wound healing has also been described. (U.S. Patent No. 5,629,292; U.S. Patent No. 5,716,935; WO 96/39164; all references herein incorporated by reference in their entirety.) A peptide agonist selective for the AT2 receptor (All has 100 times higher affinity for AT2 than ATI) has been identified. This peptide is p- aminophenylalanineό- All ["(ρ-NH₂-Phe)6- All)"] , Asp- Arg- Val-Tyr-Ile-Xaa-Pro-Phe [SEQ ID NO.36] wherein Xaa is p-NH₂-Phe (Speth and Kim, BBRC 169:997-1006 (1990)). This peptide gave binding characteristics comparable to AT2 antagonists in the experimental models tested (Catalioto, et al., Eur. J. Pharmacol. 256:93-97 (1994); Bryson, et al., Ewr. J. Pharmacol. 225:119-127 (1992)).

Many studies have focused upon AII(l-7) (All residues 1-7) or other fragments of All to evaluate their activity. AII(l-7) elicits some, but not the full range of effects elicited by AIL Pfeilschifter, et al., Eur. J. Pharmacol. 225:57-62 (1992); Jaiswal, et al., Hypertension 19 (Supp. II):II-49-II-55 (1992); Edwards and Stack, J. Pharmacol. Exper. Ther. 266:506-510 (1993); Jaiswal, et al., J. Pharmacol. Exper. Ther. 265:664-673 (1991); Jaiswal, et al., Hypertension 17:1115-1120 (1991); Portsi, et al., Br. J. Pharmacol. 111:652-654 (1994). The active All analogues, fragments of All and analogues thereof of particular interest in accordance with the present invention are characterized as comprising a sequence consisting of at least three contiguous amino acids of groups R -R in the sequence of general formula I

R¹ -R²-R³-R⁴-R⁵-R⁶-R^7"R⁸ in which R¹ and R² together form a group of formula

X-R^A-R^B-, wherein X is H or a one to three peptide group, R^Λ is suitably selected from Asp, Glu, Asn, Acpc (1- aminocyclopentane carboxylic acid), Ala, Me²Gly, Pro, Bet, Glu(NH₂), Gly, Asp(NH₂) and Sue,

R^B is suitably selected from Arg, Lys, Ala, Orn, Ser(Ac), Sar, D-Arg and D-Lys;

R³ is selected from the group consisting of Val, Ala, Leu, Lys, norLeu, He, Gly, Pro, Aib, Acpc and Tyr;

R⁴ is selected from the group consisting of Tyr, Tyr(PO₃)₂, Thr, Ser, Ala, homoSer and azaTyr; R⁵ is selected from the group consisting of He, Ala, Leu, norLeu, Val and Gly;

R⁶ is His, Arg or 6-NH₂-Phe; R⁷ is Pro or Ala; and

R⁸ is selected from the group consisting of Phe, Phe(Br), He and Tyr, excluding sequences including R⁴ as a terminal Tyr group.

Compounds falling within the category of AT2 agonists useful in the practice of the invention include the AH analogues set forth above subject to the restriction that R⁶ is p-NH₂-Phe.

Particularly preferred combinations for R^A and R^B are Asp-Arg, Asp-Lys, Glu- Arg and Glu-Lys. Particularly prefeoed embodiments of this class include the following: AIII, Arg-Val-Tyr-Ile-His-Pro-Phe [SEQ ID NO:2]; AH(3-8), also known as desl-AIII or AIV, Val-Tyr-Ile-His-Pro-Phe [SEQ ID NO:3]; AII(l-7), Asp-Arg- Val-Tyr-Ile-His-Pro {SEQ ID NO:4]; AII(2-7). Arg-Val-Tyr-Ile-His-Pro [SEQ ID NO:5]; AII(3-7), Val-Tyr-Ile-His-Pro [SEQ ID NO:6]; AII(5-8), Ile-His-Pro-Phe [SEQ ID NO:7]; AII(l-6), Asp-Arg-Val-Tyr-Ile-His [SEQ ID NO:8]; AH(l-5), Asp- Arg-Val-Tyr-Ile [SEQ ID NO:9]; AH(l-4), Asp-Arg-Val-Tyr [SEQ ID NO:10]; and AH(l-3), Asp-Arg-Val [SEQ ID NO:l 1]. Other prefeoed embodiments include: Arg- norLeu-Tyr-Ile-His-Pro-Phe [SEQ ID NO: 12] and Arg-Val-Tyr-norLeu-His-Pro-Phe [SEQ ID NO.T3]. Still another prefeoed embodiment encompassed within the scope of the invention is a peptide having the sequence Asp-Arg-Pro-Tyr-Ile-His-Pro-Phe [SEQ ID NO:31]. AII(6-8), His-Pro-Phe [SEQ ID NO: 14] and AII(4-8), Tyr-Ile-His- Pro-Phe [SEQ ID NO: 15] were also tested and found not to be effective.

A further class of particularly prefeoed compounds in accordance with the present invention consists of those with the following general structure:

ASP-ARG-R1 -R2-R3-R4-PRO-R5 wherein Rl is selected from the group consisting of Val, Pro, and Lys;

R2 is selected from the group consisting of Tyr, Tyr (PO₃)₂ and Ala;

R3 is selected from the group consisting of He, Val, Leu, norLeu and Ala; R4 is selected from the group consisting of His and Arg; and

R5 is either Phe or is absent, and wherein the active agent is not AIL

Preferred embodiments of this class of the invention include SEQ ID NO:4,

SEQ ID NO: 19, SEQ ID NO:26, SEQ ID NO:27, SEQ ID NO:31, SEQ ID NO: 32, SEQ ID NO: 34; SEQ ID NO:38, SEQ ID NO:39, and SEQ ID NO. 40. Particularly prefeoed embodiments of this class include SEQ ID NO:4, SEQ ID NO. 31, SEQ ID

NO 38, and SEQ ID NO. 39.

Another class of compounds of particular interest in accordance with the present invention are those of the general formula II R²-R³-R⁴-R⁵-R⁶-R⁷-R⁸

in which R² is selected from the group consisting of H, Arg, Lys, Ala, Orn, Ser(Ac), Sar, D-Arg and D-Lys;

R³ is selected from the group consisting of Val, Ala, Leu, norLeu, He, Gly, Pro, Aib, Acpc and Tyr;

R⁴ is selected from the group consisting of Tyr, Tyr(PO₃) , Thr, Ser, homoSer and azaTyr;

R⁵ is selected from the group consisting of He, Ala, Leu, norLeu, Val

and Gly; R⁶ is His, Arg or 6-NH₂-Phe;

R⁷ is Pro or Ala; and R⁸ is selected from the group consisting of Phe, Phe(Br), He and Tyr.

A particularly prefeoed subclass of the compounds of general formula II has

the formula

R²-R³-Tyr-R⁵-His-Pro-Phe [SEQ ID NO: 16]

wherein R², R³ and R⁵ are as previously defined. Particularly preferred is angiotensin III of the formula Arg-Val-Tyr-Ile-His-Pro-Phe [SEQ ID NO:2]. Other prefeoed compounds include peptides having the structures Arg-Val-Tyr-Gly-His- Pro-Phe [SEQ ID NO:17] and Arg-Val-Tyr-Ala-His-Pro-Phe [SEQ ID NO:18]. The fragment AII(4-8) was ineffective in repeated tests; this is believed to be due to the exposed tyrosine on the N-terminus. In the above foonulas, the standard three-letter abbreviations for amino acid residues are employed. In the absence of an indication to the contrary, the L-form of the amino acid is intended. Other residues are abbreviated as follows:

TABLE 1 Abbreviation for Amino Acids

It has been suggested that All and its analogues adopt either a gamma or a beta turn (Regoli, et al., Pharmacological Reviews 26:69 (1974). In general, it is believed that neutral side chains in position R³, R⁵ and R⁷ may be involved in maintaining the appropriate distance between active groups in positions R , R⁶ and R primarily responsible for binding to receptors and/or intrinsic activity. Hydrophobic side chains in positions R , R and R may also play an important role in the whole conformation of the peptide and/or contribute to the formation of a hypothetical hydrophobic pocket.

Appropriate side chains on the amino acid in position R may contribute to affinity of the compounds for target receptors and/or play an important role in the conformation of the peptide. For this reason, Arg and Lys are particularly prefeoed as R².

For purposes of the present invention, it is believed that R may be involved in the formation of linear or nonlinear hydrogen bonds with R⁵ (in the gamma turn model) or R (in the beta turn model). R would also participate in the first turn in a beta antiparallel structure (which has also been proposed as a possible structure). In contrast to other positions in general formula I, it appears that beta and gamma branching are equally effective in this position. Moreover, a single hydrogen bond may be sufficient to maintain a relatively stable conformation. Accordingly, R³ may suitably be selected from Val, Ala, Leu, norLeu, He, Gly, Pro, Aib, Acpc and Tyr. Furthermore, Lys has surprisingly been found to be suitable at R³ (see Examples).

With respect to R , conformational analyses have suggested that the side chain in this position (as well as in R³ and R⁵) contribute to a hydrophobic cluster believed to be essential for occupation and stimulation of receptors. Thus, R⁴ is preferably selected from Tyr, Thr, Tyr (PO₃)₂, homoSer, Ser and azaTyr. Furthermore, Ala has surprisingly been found to be suitable at the R⁴ position (See Examples). In this position, Tyr is particularly prefeoed as it may foon a hydrogen bond with the receptor site capable of accepting a hydrogen from the phenolic hydroxyl (Regoli, et al. (1974), supra).

In position R⁵, an amino acid with a β aliphatic or alicyclic chain is

particularly desirable. Therefore, while Gly is suitable in position R⁵, it is prefeoed that the amino acid in this position be selected from He, Ala, Leu, norLeu, Gly and Val. In the Al and AH analogues, fragments and analogues of fragments of particular interest in accordance with the present invention, R⁶ is His, Arg or 6-NH₂- Phe. The unique properties of the imidazole ring of histidine (e.g., ionization at physiological pH, ability to act as proton donor or acceptor, aromatic character) are believed to contribute to its particular utility as R⁶. For example, conformational models suggest that His may participate in hydrogen bond formation (in the beta model) or in the second turn of the antiparallel structure by influencing the orientation of R⁷. Similarly, it is presently considered that R⁷ should be Pro in order to provide the most desirable orientation of R⁸. In position R⁸, both a hydrophobic ring and an anionic carboxyl terminal appear to be particularly useful in binding of the analogues of interest to receptors; therefore, Tyr and especially Phe are prefeoed for purposes of the present invention.

Analogues of particular interest include the following: TABLE 2 Angiotensin II Analogues

The polypeptides of the instant invention may be synthesized by a wide variety of methods such as those set forth in J. M. Stewart and J. D. Young, Solid Phase Peptide Synthesis, 2nd ed., Pierce Chemical Co., Rockford, 111. (1984) and J. Meienhofer, Hormonal Proteins and Peptides, Vol. 2, Academic Press, New York, (1973) for solid phase synthesis and E. Schroder and K. Lubke, The Peptides, Vol. 1, Academic Press, New York, (1965) for solution synthesis. The disclosures of the foregoing treatises are incorporated by reference herein.

In general, these methods involve the sequential addition of protected amino acids to a growing peptide chain (U.S. Patent No. 5,693,616, herein incorporated by reference in its entirety). Normally, either the amino or carboxyl group of the first amino acid and any reactive side chain group are protected. This protected amino acid is then either attached to an inert solid support, or utilized in solution, and the next amino acid in the sequence, also suitably protected, is added under conditions amenable to formation of the amide linkage. After all the desired amino acids have been linked in the proper sequence, protecting groups and any solid support are removed to afford the crude polypeptide. The polypeptide is desalted and purified, preferably chromatographically, to yield the final product.

In one aspect, the present invention provides methods for the augmentation of erythropoiesis by potentiating erythropoietin-induced differentiation with angiotensinogen, angiotensin I (Al), Al analogues, Al fragments and analogues thereof, angiotensin II analogues, All fragments or analogues thereof or All AT₂ type 2 receptor agonists (ie: "active agents") as a therapeutic adjunct to erythropoietin treatment. The methods and kits of the present invention are clinically useful as a therapeutic adjunct for increasing red blood cell production in treating congenital or acquired aplastic or hypoplastic anemia.

The use of erythropoietin to promote erythropoiesis is well known in the art, as exemplified by Royet et al., U.S. Patent No. 5,482,924; Goldberg et al., U.S. Patent No. 5,188,828; Vance et al., U.S. Patent No. 5,541,158; and Baertschi et al., U.S. Patent No. 4,987,121, all references hereby incorporated in their entirety. The erythropoietin dosage regimen may vary widely, but can be determined routinely by a physician using standard methods. Dosage levels of the order of between about 1 EPO unit/kg and about 5,000 EPO units/kg body weight are useful for all methods of use disclosed herein.

In one embodiment, the effects of the active agents on the growth of erythroid progenitors in vitro are tested using the colony formation assay. The assay consists of growing erythroid progenitor cells in a semi-solid medium (methylcellulose) for two weeks (Yu et al., U.S. Patent No. 5,032,507). Conditioned medium consisting of phytohemagglutinin-treated lymphocytes (PHA-LCM) is supplemented with erythropoietin and preferably, between about 0.1 ng/ml and about 10 mg/ml of the active agents.

The growth of erythroid precursors termed BFU-E (burst forming units erythroid) is monitored by identification and counting of the colonies under an

inverted microscope as well as by staining of colonies (Yu et al., U.S. Patent No. 5,032,507). The number of mixed colonies represents the number of earlier progenitor cells (containing erythroid as well as one or more other lineage cells). In another embodiment, erythropoiesis is augmented ex vivo by obtaining a sample of bone marrow cells, as is known in the art, potentiating erythropoietin- induced differentiation with the active agents of the invention and infusing the treated cells back into the patient. In a prefeoed embodiment, bone maoow cells are isolated from peripheral blood samples via standard techniques (U.S. Patent Nos. 4,987,121, 5,104,653; hereby incorporated by reference in their entirety). 2 x 10⁶ bone marrow cells are seeded in culture dishes in appropriate medium, such as modified Dulbecco's medium (IMDM) supplemented with (final concentration): horse serum (15%), fetal calf serum (5%), Fe saturated transferrin (0.4 mg/ml) hydrocortisone, penicillin 100 u/ml, and streptomycin (0.1 mg/ml) (Royet et al., U.S. Patent No. 5,482,924). An adherent cell monolayer is formed. After 15 days, the non adherent cells are removed and fresh bone marrow is re-seeded in the presence of 0.1 U/ml of erythropoietin (EPO) and, preferably, between about 0.1 ng/ml and about 10 mg/ml of the active agents of the invention. The cells are expanded for a period of between 2 and 21 days with subsequent medium changes as required. Prior to reinfusion into the subject the cells are examined microscopically to verify the absence of contamination. The cells are rinsed to remove all traces of culture fluid, resuspended in an appropriate medium and then pelleted and rinsed several times. After the final rinse, the cells are resuspended at between 0.7 x 10⁶ and 50 x 10⁶ cells per ml in an appropriate medium and reinfused into a subject. Erythropoiesis is monitored by red cell count or hemoglobin concentration with time (Yu et al., U.S. Patent No. 5,032,507, herein incorporated by reference in its entirety). For use in increasing erythropoiesis in vivo, the active agents may be administered by any suitable route, including orally, parentally, by inhalation spray, rectally, transdermally, or topically in dosage unit formulations containing conventional pharmaceutically acceptable carriers, adjuvants, and vehicles. The term parenteral as used herein includes, subcutaneous, intravenous, intra-arterial, intramuscular, intrasternal, intratendinous, intraspinal, intracranial, intrathoracic, infusion techniques or intraperitoneally.

Transdermal means including, but not limited to, transdermal patches may be utilized to deliver the active agents to the treatment site. Transdermal formulations may be prepared by incorporating the active agent in a thixotropic or gelatinous carrier including, but not limited to a cellulose medium, e.g., methyl cellulose or hydroxyethyl cellulose, with the resulting formulation then being packed in a transdermal device adapted to be secured in dermal contact with the skin of a wearer.

The active agents may be made up in a solid form (including granules, powders or suppositories) or in a liquid form (e.g., solutions, suspensions, or emulsions). The active agents may be subjected to conventional pharmaceutical operations such as sterilization and/or may contain conventional adjuvants, such as preservatives, stabilizers, wetting agents, emulsifiers, buffers etc.

While the active agents can be administered as the sole active pharmaceutical agent, they can also be used in combination with one or more other compounds.

When administered as a combination, the active agent(s) and compound(s) can be formulated as separate compositions that are given at the same time or different times, or the active agent(s) and compound(s) can be given as a single composition. For administration, the active agents are ordinarily combined with one or more adjuvants appropriate for the indicated route of administration. The active agents may be admixed with lactose, sucrose, starch powder, cellulose esters of alkanoic acids, stearic acid, talc, magnesium stearate, magnesium oxide, sodium and calcium salts of phosphoric and sulphuric acids, acacia, gelatin, sodium alginate, polyvinylpyoolidine, and/or polyvinyl alcohol, and tableted or encapsulated for conventional administration. Alternatively, the compounds of this invention may be dissolved in saline, water, polyethylene glycol, propylene glycol, carboxymethyl cellulose colloidal solutions, ethanol, corn oil, peanut oil, cottonseed oil, sesame oil, tragacanth gum, and/or various buffers. Other adjuvants and modes of administration are well known in the pharmaceutical art. The carrier or diluent may include time delay material, such as glyceryl monostearate or glyceryl distearate alone or with a wax, or other materials well known in the art.

Formulations suitable for topical administration include liquid or semi-liquid preparations suitable for penetration through the skin (e.g., liniments, lotions, ointments, creams, or pastes) and drops suitable for administration to the eye, ear, or nose.

The dosage regimen for augmenting erythropoiesis with the active agents is based on a variety of factors, including the type of injury, the age, weight, sex, medical condition of the individual, the severity of the condition, the route of administration, and the particular compound employed. Thus, the dosage regimen may vary widely, but can be determined routinely by a physician using standard methods. Dosage levels of the order of between 0.1 ng/kg and 10 mg/kg of the active agents per body weight are useful for all methods of use disclosed herein. The treatment regime will vary depending on the disease being treated, based on a variety of factors, including the type of injury, the age, weight, sex, medical condition of the individual, the severity of the condition, the route of administration, and the particular compound employed. In a preferred embodiment of the present invention, the active agents are administered intravenously. A suitable dose of the active agents is preferably between about 0.1 ng/kg and about 10 mg/kg administered twice daily. For topical administration, the active ingredient may comprise from 0.001% to 10% w/w, e.g., from 1% to 2% by weight of the formulation, although it may comprise as much as 10% w/w, but preferably not more than 5% w/w, and more preferably from 0.1% to 1% of the formulation.

In another aspect, the present invention provides a novel peptide with erythropoiesis-promoting activity, consisting of the peptide with the sequence Asp- Arg-Lys-Tyr-Ile-His-Pro-Phe (SEQ ID NO:39). A further object of the present invention is to provide pharmaceutical compositions comprising the active agents as an ingredient for use in the method of the invention. The compositions comprise the active agents together with erythropoietin and a pharmaceutically acceptable carrier, this term including any carrier which does not interfere with the effectiveness of the biological activity of the active agents and erythropoietin, and which is not toxic to the host to which it is administered. Dosage and administration of the pharmaceutical compositions will vary depending on the disease being treated, based on a variety of factors, including the type of injury, the age, weight, sex, medical condition of the individual, the severity of the condition, the route of administration, and the particular compound employed, as above. Thus, the dosage regimen may vary widely, but can be determined routinely by a physician using standard methods.

In a further aspect, the present invention provides kits promoting erythropoiesis, wherein the kits comprise an effective amount of the active agent, and instructions for using the amount effective of active agent as a therapeutic adjunct. In a prefeoed embodiment, the kit further comprises a pharmaceutically acceptable carrier, such as those adjuvants described above. In another prefeoed embodiment, the kit further comprises a means for delivery of the active agent to a mammal. Such devices include, but are not limited to matrical or micellar solutions, polyethylene glycol polymers, carboxymethyl cellulose preparations, crystalloid preparations (e.g., saline, Ringer's lactate solution, phosphate-buffered saline, etc.), viscoelastics, polyethylene glycols, and polypropylene glycols.

In a further preferred embodiment, the kits also comprise an amount of erythropoietin effective to accelerate erythropoiesis. In another aspect of the present invention, an improved cell culture medium is provided for the promotion of erythropoiesis, wherein the improvement comprises addition to the cell culture medium of an effective amount of the active agents of the invention. Any cell culture media that can support erythropoiesis can be used with the present invention. Such cell culture media include, but are not limited to Basal Media Eagle, Dulbecco's Modified Eagle Medium, Iscove's Modified Dulbecco's

Medium, McCoy's Medium, Minimum Essential Medium, F-10 Nutrient Mixtures,

Opti-MEM® Reduced-Serum Medium, and RPMI Medium, or combinations thereof.

The improved cell culture medium can be supplied in either a concentrated (ie:

10X) or non-concentrated form, and may be supplied as a liquid, a powder, or a lyophilizate. The cell culture may be either chemically defined, or may contain a serum supplement. Culture media and serum supplements are commercially available from many sources, such as GIBCO BRL (Gaithersburg, MD) and Sigma (St. Louis, MO). The present invention, by providing methods and pharmaceutical compositions for augmenting erythropoiesis, will greatly increase the clinical benefits of treatment for congenital or acquired aplastic or hypoplastic anemia; amelioration of anemia associated with cancer, AIDS, chemotherapy, radiotherapy, bone marrow transplantation and chronic diseases. The present invention may be better understood with reference to the accompanying examples that are intended for purposes of illustration only and should not be construed to limit the scope of the invention, as defined by the claims appended hereto.

Example 1. All and All analogue and fragment effect on erythroid progenitor formation

CD34+ cells were isolated from human cord blood by immunomagnetic chromatography using an antibody cocktail (Stem Cell Technologies, Vancouver BC) consisting of the following cell surface proteins: glycophorin A, CD56, CD66b, CD3, CD24, CD 14, CD2, CD 19, and CD 16. Enriched cells were cultured at 37° at 5% CO₂ and air for 6 days in medium containing serum-free StemSpan (Stem Cell Technologies), 3 IU/ml human erythropoietin (EPO), 20 ng/ml stem cell factor, 20 ng/ml interleukin 3, and 20 ng/ml GM-CSF. The cells were harvested, counted and cultured in 96 well plates at a density of 50,000 cells per well in the same medium containing from 0 to 10 μg/ml of All, AH analogues, or All fragments. The peptides tested, and the figure showing the data received in those tests, are listed in Table 3. After 3 additional days in suspension culture (day 9), the cells were washed to remove the peptides and cultured to assess colony formation. The culture medium contained 0.9% methylcellulose in Iscove's MDM with 30% fetal calf serum, 1% bovine serum albumin, 10 μM 2-mercaptoethanol, 2mM L-glutamine, 10% Agar Leukocyte Conditioned Medium with 3 IU/ml EPO. On days 2, 4, 9, and 14 the number and size of colonies was assessed as well as the number of BFU-E formed (burst forming units-erythroid) as a measure of erythropoiesis.

Table 3. Designation fo r Peptides Tested

Name Abbreviation Sequence Figure SEQ ID

1GD Ala⁴-AH(l-7) DRVAfflP 1 SEQ ID NO. 18

GSD 24B Pro³-AII DRPYIHPF 2 SEQ ID NO. 31

2GD Pro³-AH(l-7) DRPYIHP 3 SEQ ID NO. 38

5GD Lys³-AII(l-7) DRKYIHP 4 SEQ ID NO 39

AII(l-7) DRVYIHP 5 SEQ ID NO. 4

AH DRVYfflPF 6 SEQ ID NO. 1

The data from these experiments are presented in Figures 1-6 and show that each of the peptides tested increased the number of BFU-E formed relative to control where no peptide was added. Each of the peptides also increased the size of the colonies assessed (data not shown). Therefore, these data demonstrate that each of the peptides tested can be used to accelerate erythroid progenitor formation, and thus to promote erythropoiesis. The methods and kits of the present invention are clinically useful as a therapeutic adjunct for increasing red blood cell production in treating congenital or acquired aplastic or hypoplastic anemia. The present invention is not limited by the aforementioned particular preferred embodiments. It will occur to those ordinarily skilled in the art that various modifications may be made to the disclosed prefeoed embodiments without diverting from the concept of the invention. All such modifications are intended to be within the scope of the present invention.

Claims

We claim:

1. A method for augmenting erythropoiesis comprising contacting erythroid progenitor cells with an amount effective to augment erythropoiesis of at least one active agent comprising a sequence consisting of at least three contiguous amino acids of groups R^R⁸ in the sequence of general formula I

R¹ -R²-R³-R⁴-R⁵-R⁶-R^7"R⁸ in which R and R together form a group of formula

X-R^A-R^B-, wherein X is H or a one to three peptide group R^Λ is selected from Asp, Glu, Asn, Acpc, Ala, Me²Gly, Pro, Bet,

Glu(NH₂), Gly, Asp(NH₂) and Sue;

R^B is selected from Arg, Lys, Ala, Orn, Ser(Ac), Sar, D-Arg and D- Lys;

R³ is selected from the group consisting of Val, Ala, Leu, norLeu, He, Gly, Pro, Aib, Acpc, Lys and Tyr;

R⁴ is selected from the group consisting of Tyr, Tyr(PO₃)₂, Thr, Ser, Ala, homoSer and azaTyr;

R⁵ is selected from the group consisting of He, Ala, Leu, norLeu, Val

and Gly; R⁶ is His, Arg or 6-NH₂-Phe;

R is Pro or Ala; and

R⁸ is selected from the group consisting of Phe, Phe(Br), He and Tyr, excluding sequences including R⁴ as a terminal Tyr group, and wherein the active agent is not AIL

2. The method of claim 1 wherein the active agent is selected from the group consisting of angiotensinogen, SEQ ID NO:2, SEQ ID NO:3, SEQ ID NO:4, SEQ ID NO:5, SEQ ID NO:6, SEQ ID NO:7, SEQ ID NO:8, SEQ ID NO:9, SEQ ID NO: 10, SEQ ID NO:l l, SEQ ID NO:12, SEQ ID NO:13, SEQ ID NO:16, SEQ ID NO:17, SEQ ID NO:18, SEQ ID NO:19, SEQ ID NO:20, SEQ ID NO:21, SEQ ID NO:22, SEQ ID NO:23, SEQ ID NO:24, SEQ ID NO:25, SEQ ID NO:26, SEQ ID NO:27, SEQ ID NO:28, SEQ ID NO:29, SEQ ID NO:30, SEQ ID NO:31, SEQ ID NO: 32, SEQ ID NO:33, SEQ ID NO: 34; SEQ ID NO:35, SEQ ID NO:36, SEQ ID NO:37, SEQ ID NO:38, and SEQ ID NO:39.

3. The method of claim 1 wherein the concentration of active agent is between about 0.1 ng/kg and about 10.0 mg/kg.

4. A method for augmenting erythropoiesis comprising contacting erythroid progenitor cells with an amount effective to augment erythropoiesis of an active agent comprising a sequence of the following general formula: ASP-ARG-R1-R2-R3-R4-PRO-R5 wherein Rl is selected from the group consisting of Val, Pro, and Lys;

R2 is selected from the group consisting of Tyr, Tyr (PO₃)₂ and Ala;

R3 is selected from the group consisting of He, Val, Leu, norLeu and Ala;

R4 is selected from the group consisting of His and Arg; and R5 is either Phe or is absent, and wherein the active agent is not AIL

5. The method of claim 4 wherein the active agent is selected from the group consisting of SEQ ID NO:4, SEQ ID NO: 19, SEQ ID NO:26, SEQ ID NO:27, SEQ ID NO:31, SEQ ID NO: 32, SEQ ID NO: 34; SEQ ID NO:38, and SEQ ID NO:39.

6. The method of claim 4 wherein the active agent is selected from the group consisting of SEQ ID NO:4, SEQ ID NO. 31, SEQ ID NO 38, and SEQ ID NO. 39.

7. The method of claim 4 wherein the concentration of active agent is between about 0.1 ng/kg and about 10.0 mg/kg.

8. A pharmaceutical composition comprising an amount effective to augment erythropoiesis of at least one active agent comprising a sequence consisting of at least three contiguous amino acids of groups R -R in the sequence of general formula I

R^!-R²-R³-R⁴-R⁵-R⁶-R⁷-R⁸

1 in which R and R together form a group of formula X-R^A-R^B-, wherein X is H or a one to three peptide group

R^A is selected from Asp, Glu, Asn, Acpc, Ala, Me²Gly, Pro, Bet, Glu(NH₂), Gly, Asp(NH₂) and Sue;

R^B is selected from Arg, Lys, Ala, Orn, Ser(Ac), Sar, D-Arg and D- Lys;

R⁶ is His, Arg or 6-NH₂-Phe; R⁷ is Pro or Ala; and R⁸ is selected from the group consisting of Phe, Phe(Br), He and Tyr, excluding sequences including R⁴ as a terminal Tyr group, wherein the active agent is not All; an amount of erythropoietin effective to stimulate erythropoiesis; and a pharmaceutically acceptable carrier.

9. The pharmaceutical composition of claim 8 wherein the active agent is selected from the group consisting of angiotensinogen, SEQ ID NO:2, SEQ ID NO:3, SEQ ID NO:4, SEQ ID NO:5, SEQ ID NO:6, SEQ ID NO:7, SEQ ID NO:8, SEQ ID NO:9, SEQ ID NO:10, SEQ ID NO:l l, SEQ ID NO:12, SEQ ID NO:13, SEQ ID NO: 16, SEQ ID NO: 17, SEQ ID NO: 18, SEQ ID NO: 19, SEQ ID NO:20, SEQ ID NO:21, SEQ ID NO:22, SEQ ID NO:23, SEQ ID NO:24, SEQ ID NO:25, SEQ ID NO:26, SEQ ID NO:27, SEQ ID NO:28, SEQ HD NO:29, SEQ ID NO:30, SEQ ID NO:31, SEQ ID NO: 32, SEQ ID NO:33, SEQ HD NO: 34; SEQ ID NO:35, SEQ ID NO:36, SEQ ID NO:37, SEQ ID NO:38, and SEQ ID NO:39.

10. The pharmaceutical composition of claim 8 wherein the concentration of active agent is between about 0.1 ng/kg and about 10.0 mg/kg.

11. A pharmaceutical composition comprising an amount effective to augment erythropoiesis of an active agent comprising a sequence of the following general formula: ASP-ARG-R1-R2-R3-R4-PRO-R5 wherein Rl is selected from the group consisting of Val, Pro, and Lys;

R2 is selected from the group consisting of Tyr, Tyr (PO₃)₂ and Ala;

R3 is selected from the group consisting of He, Val, Leu, norLeu and Ala;

R4 is selected from the group consisting of His and Arg; and R5 is either Phe or is absent, and wherein the active agent is not AIL an amount of erythropoietin effective to stimulate erythropoiesis; and a pharmaceutically acceptable carrier.

12. The pharmaceutical composition of claim 11 wherein the active agent is selected from the group consisting of SEQ ID NO:4, SEQ ID NO: 19, SEQ ID NO:26, SEQ ID NO:27, SEQ ID NO:31, SEQ ID NO: 32, SEQ ID NO: 34; SEQ HD NO:38, and SEQ ID NO:39.

13. The pharmaceutical composition of claim 11 wherein the active agent is selected from the group consisting of SEQ ID NO:4, SEQ ID NO. 31, SEQ ID NO

38, and SEQ ID NO. 39.

14. The pharmaceutical composition of claim 11 wherein the concentration of active agent is between about 0.1 ng/kg and about 10.0 mg/kg.

15. A kit for augmenting erythropoiesis, comprising: (a) an amount effective to augment erythropoiesis of at least one active agent comprising a sequence consisting of at least three contiguous amino acids of groups R^!-R⁸ in the sequence of general formula I

R¹-R²-R³-R⁴-R⁵-R⁶-R⁷-R⁸ in which R and R together form a group of formula X-R^A-R^B-, wherein X is H or a one to three peptide group

R^A is selected from Asp, Glu, Asn, Acpc, Ala, Me²Gly, Pro, Bet, Glu(NH₂), Gly, Asp(NH₂) and Sue; R^B is selected from Arg, Lys, Ala, Orn, Ser(Ac), Sar, D-Arg and D-

Lys;

R³ is selected from the group consisting of Val, Ala, Leu, norLeu, He,

Gly, Pro, Aib, Acpc, Lys and Tyr;

R⁵ is selected from the group consisting of He, Ala, Leu, norLeu, Val and Gly;

R⁶ is His, Arg or 6-NH₂-Phe; R⁷ is Pro or Ala; and

R⁸ is selected from the group consisting of Phe, Phe(Br), He and Tyr, excluding sequences including R⁴ as a terminal Tyr group, wherein the active agent is not AH; and (b) instructions for using the amount effective of active agent to augment erythropoiesis.

16. The kit of claim 15 wherein the active agent is selected from the group consisting of angiotensinogen, SEQ ID NO:2, SEQ ID NO:3, SEQ ID NO:4, SEQ HD NO:5, SEQ ID NO:6, SEQ ID NO:7, SEQ ID NO:8, SEQ ID NO:9, SEQ ID NO: 10, SEQ HD NO:l l, SEQ ID NO:12, SEQ ID NO:13, SEQ ID NO:16, SEQ ID NO:17, SEQ HD NO: 18, SEQ ID NO: 19, SEQ ID NO:20, SEQ ID NO:21, SEQ ID NO:22, SEQ ID NO:23, SEQ ID NO:24, SEQ HD NO:25, SEQ ID NO:26, SEQ ID NO:27, SEQ ID NO:28, SEQ ID NO:29, SEQ HD NO:30, SEQ ID NO:31, SEQ ID NO: 32, SEQ HD NO:33, SEQ ID NO: 34; SEQ ID NO:35, SEQ ID NO:36, SEQ ID NO:37, SEQ HD NO:38, and SEQ ID NO:39.

17. The kit of claim 15 wherein the concentration of active agent is between about 0.1 ng/ml and about 10.0 mg/ml.

18. A kit for augmenting erythropoiesis comprising an amount effective to augment erythropoiesis of an active agent comprising a sequence of the following general formula:

R2 is selected from the group consisting of Tyr, Tyr (PO₃) and Ala;

R5 is either Phe or is absent, and wherein the active agent is not AH; and

(b) instructions for using the amount effective of active agent to augment erythropoiesis.

19. The kit of claim 18 wherein the active agent is selected from the group consisting of SEQ ID NO:4, SEQ ID NO: 19, SEQ ID NO:26, SEQ ID NO:27, SEQ ID NO:31, SEQ ID NO: 32, SEQ ID NO: 34; SEQ ID NO:38, and SEQ ID NO:39.

20. The kit of claim 18 wherein the active agent is selected from the group consisting of SEQ ID NO:4, SEQ ID NO. 31, SEQ ID NO 38, and SEQ ID NO. 39.

21. The kit of claim 18 wherein the concentration of active agent is between about 0.1 ng/ml and about 10.0 mg/ml.

22. An improved cell culture medium for promotion of erythropoiesis, wherein the improvement comprises addition to the cell culture medium an amount effective to promote erythropoiesis of at least one active agent comprising a sequence consisting of at least three contiguous amino acids of groups R'-R⁸ in the sequence of general

formula I

R¹ -R²-R³-R⁴-R⁵-R⁶-R^7"R⁸ in which R¹ and R² together form a group of formula X-R^A-R^B-, wherein X is H or a one to three peptide group,

R^A is suitably selected from Asp, Glu, Asn, Acpc (1- aminocyclopentane carboxylic acid), Ala, Me²Gly, Pro, Bet, Glu(NH₂), Gly, Asp(NH₂) and Sue, R^B is suitably selected from Arg, Lys, Ala, Orn, Ser(Ac), Sar, D-Arg and D-Lys;

R⁶ is His, Arg or 6-NH₂-Phe; R⁷ is Pro or Ala; and R⁸ is selected from the group consisting of Phe, Phe(Br), He and Tyr, excluding sequences including R⁴ as a terminal Tyr group, and wherein the active agent is not AIL

23. The improved cell culture medium of claim 22 wherein the active agent is selected from the group consisting of angiotensinogen, SEQ ID NO:2, SEQ ID NO:3, SEQ ID NO:4, SEQ HD NO:5, SEQ ID NO:6, SEQ ID NO:7, SEQ HD NO:8, SEQ ID NO:9, SEQ ID NO: 10, SEQ ID NO:l l, SEQ ID NO:12, SEQ HD NO:13, SEQ ID NO: 16, SEQ ID NO:17, SEQ HD NO:18, SEQ ID NO:19, SEQ ID NO:20, SEQ ID NO:21, SEQ ID NO:22, SEQ ID NO:23, SEQ ID NO:24, SEQ ID NO:25, SEQ ID NO:26, SEQ ID NO:27, SEQ ID NO:28, SEQ ID NO:29, SEQ ID NO:30, SEQ ID NO:31, SEQ ID NO: 32, SEQ ID NO:33, SEQ ID NO: 34; SEQ ID NO:35, SEQ ID NO:36, SEQ ID NO:37, SEQ ID NO:38, and SEQ ID NO:39.

24. The improved cell culture medium of claim 22 wherein the concentration of active agent is between about 0.1 ng/ml and about 10.0 mg/ml.

25. An improved cell culture medium for promotion of erythropoiesis, wherein the improvement comprises addition to the cell culture medium an amount effective to promote erythropoiesis of at least one active agent comprising a sequence of the following general formula:

ASP-ARG-Rl -R2-R3-R4-PRO-R5 wherein Rl is selected from the group consisting of Val, Pro, and Lys;

R2 is selected from the group consisting of Tyr, Tyr (PO )₂ and Ala;

R3 is selected from the group consisting of He, Val, Leu, norLeu and Ala;

R4 is selected from the group consisting of His and Arg; and

R5 is either Phe or is absent, and wherein the active agent is not AIL

26. The improved cell culture medium of claim 25 wherein the active agent is selected from the group consisting of SEQ ID NO:4, SEQ ID NO: 19, SEQ ID NO:26, SEQ ID NO:27, SEQ ID NO:31, SEQ HD NO: 32, SEQ HD NO: 34; SEQ HD NO:38, and SEQ HD NO:39.

27. The improved cell culture medium of claim 25 wherein the active agent is selected from the group consisting of SEQ ID NO:4, SEQ ID NO. 31, SEQ ID NO 38, and SEQ ID NO. 39.

28. A novel peptide with erythropoiesis promoting activity, consisting of the sequence Asp-Arg-Lys-Tyr-Ile-His-Pro-Phe [SEQ ID NO:39].

29. A pharmaceutical composition comprising the peptide of claim 28 and a pharmaceutically acceptable carrier.

30. The pharmaceutical composition of claim 29 further comprising an amount of erythropoietin effective to stimulate erythropoiesis.