Antineoplaston A was further purified and yielded antineoplastons A1, A2, A3, A4, and A5. These mixtures of 7 to 13 peptides were patented in 1985.In vitro tissue culture studies and in vivo toxicity studies in animal models were performed for antineoplastons A1 through A5. According to the developer, each individual fraction had a higher level of antitumor activity and lower toxicity level than antineoplaston A.
Phase I trials of this antineoplaston group in patients with various advanced cancers showed A2 as contributing to the highest tumor response rate, so it was selected for further study.
The active compound in A2 was found to be 3-phenylacetylamino-2,6-piperinedione, which was named antineoplaston A10. From antineoplaston A10, three other compounds have been derived:
- AS2-5, which is phenylacetylglutamine (PAG).
- AS2-1, which is a 4:1 mixture of phenylacetic acid (PA) and PAG.
- A5, which is PA and an aromatic fatty acid.
Other antineoplastons (A3, A4, A10-1, AS5) were added to this group after further studies.[2,3,4]
There have been no independent analyses of which amino acids comprise the antineoplastons used in any of the reported studies.
Antineoplastons are administered by different methods. Antineoplaston A has been given intravenously, intramuscularly, rectally, topically, intrapleurally, and by bladder instillation. Presently, antineoplastons A10, AS2-5, AS2-1, A2, A3, and A5 are given orally or by injection.[8,9,10,11,12,13,14,15,16,17,18,19,20]
Critical opposition to antineoplaston therapy and its developer have appeared in the published literature. A basic criticism of the developer's work is that although he has put forth a theory of peptides inducing cell differentiation, there is no published evidence that he has experimentally tested the hypothesis that information-bearing peptides could normalize cancer cells. Although some articles attempt to demonstrate that antineoplastons (specifically, antineoplaston A10) can bind to DNA at certain sites, this is an extrapolation from three-dimensional molecular models of DNA and A10 and does not demonstrate that this binding actually occurs.[21,22,23]
Other criticism focuses on the form of antineoplastons. Although the active fraction, antineoplaston A10, is insoluble in aqueous solutions, the developer has stated that it is present in body fluids.
Antineoplastons AS2-5 and AS2-1 are derived from A10. Antineoplaston AS2-5 is PAG, and AS2-1 is a 4:1 mixture of PA and PAG. Because it is a strong acid, PA would exhibit cytotoxicity in vitro if in high enough concentration and not neutralized.
The active component of antineoplaston A10 is 3-phenylacetylamino-2,6-piperidinedione. Reagents necessary for the synthesis of this antineoplaston compound are readily available internationally from any chemical supply company. The developer retains patents on antineoplaston compounds and their use when administered pharmaceutically to inhibit the growth of neoplastic cells.[6,25]