DESC:Field of the invention
The present invention relates to a storage stable D-Cycloserine. The invention also relates to a process for preparation of the said storage stable D-Cycloserine.

Background and the prior art
D-Cycloserine, (R)-4-amino-1, 2-oxazolidin-3-one represented by formula (I) is a natural product of Streptomyces orchidaceus and Streptomyces garyphalus, which has been known in tuberculosis therapy since the late 1950s. It is indicated in the treatment of active pulmonary and extra pulmonary tuberculosis.

D-Cycloserine has also been widely introduced to neuropsychiatric studies, since its central active mechanism as a partial N-methyl-D-aspartate (NMDA) receptor agonist has been found.

D-Cycloserine discovered as a metabolite product of new species of Streptomyces (S. orchidaceus and S. garyphalus) is first reported in 1955 by Kuhel Jr. et al in J. Am. Chem. Soc. Vol. 77, 2344 (1955).

D-Cycloserine is produced by fermentation as well as by synthetic means. Several methodologies for production and purification of D-Cycloserine have been reported in the literature.

US2773878 discloses the production of D-Cycloserine by fermentation method from a novel strain of the known species of microorganism S. lavendulae.

Other patent documents disclosing preparation of D-Cycloserine by fermentation involving a Cycloserine producing microorganism include GB 768007 and US 3090730.

Recovery and purification of antibiotic D-Cycloserine from impure aqueous nutrient medium/fermentation broth is described in US 2789983 and GB787740.

One of the first chemical synthesis of Cycloserine has been described by Stammer et al in J. Am. Chem. Soc., 77, 2347 (1955), starting from methyl ester of dl-serine, condensation of the same with ethyl imino benzoate into the corresponding oxazoline, conversion of the latter into the corresponding hydroxamic acid, chlorination followed by opening of the oxazoline ring and re-condensation of the chloro hydroxamic acid into substituted isoxazolidone. The latter is then opened again with hydrochloric acid and the methyl ester of a ß-amino-oxyalanine is obtained, from which racemic Cycloserine is finally obtained with loss of the benzoic radical. Racemic Cycloserine thus obtained is resolved into its optical isomers by means of tartaric acid.

Many chemical syntheses of D-Cycloserine from serine and its derivatives have been described in the literature US2772280, US2840565, GB799066, GB791847, SU163622, US2794022, US2929836, GB856393, SU202148, KR2012131646 and CN 105646385.

CN 105198825 A describes a method for the preparation of D-Cycloserine with high optical purity via amidation of D-serine with 2, 2, 2-trifluoro-acetic acid ethyl ester followed by reaction with hydroxylamine hydrochloride, intramolecular heterocyclization, and hydrolysis.

Purification of the antibiotic D-Cycloserine has been extensively studied and described in US 2845433, JP34003795 JP 35004543 JP 35015599 JP 35005293 CN 102382072 involving recrystallization from organic solvents and acid-base purification method.

D-Cycloserine is slightly hygroscopic and degrades upon exposure to a humid atmosphere; decomposition being faster at higher temperatures. Therefore, D- Cycloserine is recommended to be stored in a tightly closed container at temperatures below ambient preferably in the presence of a desiccant.

Transformation of D-Cycloserine into the dimer, D-3, 6- bis (aminooxymethyl)-2,5-diketopiperazine represented by formula (II), impurity in the presence of traces of water is responsible for the degradation and consequent loss in effectiveness.

Studies on stability of D-Cycloserine have been done as a pharmaceutical preparation like tablet and capsule as described in Rao et al in Bull. Wld. Hlth. Org., 39, 781-789 (1968) and in Ind. Jour. Med. Res., 57, 3, 550-566, (1969).

The stability of D-Cycloserine has also been studied in the solid state as well as aqueous phase under different temperatures humidity, pH etc. conditions to establish its storage conditions.

Appropriate packing of a bulk drug/active pharmaceutical ingredient is a necessity. The bulk drugs should be packed based on their nature to avoid the degradation during storage.

The stability of a bulk drug/active pharmaceutical ingredient is one of the most important criteria required by most regulatory agencies. Therefore one needs to demonstrate that in the powder form and even after formulation the quality of the bulk drug/active pharmaceutical ingredient or its solid form is intact over a period of shelf life.

The degradation in the quality of a bulk drug/active pharmaceutical ingredient mostly occurs because of changes in humidity, temperature or oxidative degradation conditions.
Therefore it is imperative that all possible precautions should be taken to prevent deterioration of D-Cycloserine during storage.

Object of the invention
It is an object of the present invention to provide a storage stable D-Cycloserine.

It is an object of the present invention to provide a process for preparation of the said storage stable D-Cycloserine using an efficient packing system. Such an efficient packing system provides storage of D-Cycloserine so that its potency is maintained.

It is another object of the present invention to provide an efficient packing system for storage of D-Cycloserine to limit formation of dimer impurity to not more than 0.2%.

It is yet another object of the present invention to provide an efficient packing system for storage of D-Cycloserine at ambient temperature.

Description of the invention
It is thus an object of the present invention to provide storage stable D-Cycloserine.

The present invention provides a process for preparing the said storage stable D-Cycloserine comprising a packing system to enhance the stability of D-Cycloserine during storage.

In a preferred aspect the present invention provides a packing system for storage of D-Cycloserine at ambient temperature without significant degradation.

This is provided by multiple packing, inert atmosphere and applying vacuum, which provides additional benefits in presence of desiccants.

A desiccant is a hygroscopic substance that induces or sustains a state of dryness. The desiccant includes activated carbon, silica, zeolites, molecular sieves, hydrogels, calcium oxide and diatomaceous earth. The use of desiccant materials used will depend upon the humidity level of the environment. The desiccant is available in the form of a sachet, cartridge or canister.

The packing material for packing system comprises of air as well as moisture impermeable material so that vacuum created during packing is maintained throughout the shelf life of the bulk drug/active pharmaceutical ingredient.

The packing material is chosen from Polyethylene (PE), bi-axially oriented polypropylene (BOPP), polyethylene terpthalate (PET), oriented polyamide (OPA), aluminum foil, or a blend of these polymers or a laminated structure of these polymers. Possible structures of the laminate are PET/aluminum foil/PE, or OPA/PET/PE, or Triple Laminate Sunlight Barrier (TLSB) or quad laminate ultra-barrier (QLUB) bag and various other permutations and combinations thereof.

The laminate structure would primarily depend on moisture/light barrier required by the bulk drug /active pharmaceutical ingredient. As the polyethylene based resin, there can be enlisted but are not limited to linear low density polyethylene (LLDPE), high density polyethylene (HDPE), low density polyethylene (LDPE), High Molecular High Density Polyethyene (HM-HDPE) polypropylene, acrylonitrile, polyamide, polyvinylidinefluoride (PVDF), ethylene acrylic acid, ethylene/methacrylic acid (E/MAA) copolymer, polypropylene lacquer, polyacetal and copolymers thereof.

In one embodiment of the present invention categorized as Packing A condition, wherein the D-Cycloserine dry powder is first packed in a low density polythene (LDPE) bag and heat sealed under vacuumized packing condition.

The LDPE bag is then placed in another inner LDPE bag and twist and tied with a plastic fastener. The inner LDPE bag is thereafter placed in a Triple laminated aluminum bag (TLAB) along with silica sachet/pouch/bag containing silica calculated as NLT 1 Kg (small pouch/bag of 50g to 250g evenly distributed in TLAB) for 25 kg D-Cycloserine dry powder and heat sealed under nitrogen.

The TLAB is finally stored in a high density polyethylene (HDPE)/ high molecular-high density polyethylene (HM- HDPE) drum or container.

In another embodiment the stability of the D-Cycloserine dry powder of the present invention under Packing A conditions is studied at 25 + 2°C /65 + 5%RH and at 40 + 2°C/75 + 5%RH and the outcome of the study is as provided in the following Table-1 and Table-2, respectively.

Table-1: Stability at 25 + 2°C /65 + 5%RH

S.N Stability condensation
product
(NMT 0.8) Dimer
(NMT 0.2%) Assay
(98.5-101.5 %)
SOR
(108-114°) Remarks
1. Initial 0.07 BDL 99.8 113 Complies
1 M 0.07 BDL 100.4 113 Complies
2 M 0.07 BQL 100.6 112 Complies
3 M 0.10 BQL 100.4 113 Complies
6 M 0.18 0.10 100.1 113 Complies
2. Initial 0.05 BDL 99.9 113 Complies
1 M 0.05 BDL 100.3 113 Complies
2 M 0.05 BQL 100.1 113 Complies
3 M 0.05 BQL 100.4 113 Complies
6 M 0.09 0.05 100.3 113 Complies
3. Initial 0.01 BDL 99.5 113 Complies
1 M 0.06 BQL 100.5 112 Complies
3 M 0.06 0.09 100.6 113 Complies
6 M 0.15 0.12 99.3 111 Complies

Table-2: Stability at 40 + 2°C/75 + 5%RH

S.N Stability condensation
product
(NMT 0.8) Dimer
(NMT 0.2%) Assay
(98.5-101.5 %)
SOR
(108-114°) Remarks
1. Initial 0.07 BDL 99.8 113 Complies
1 M 0.08 BDL 100.2 112 Complies
2M 6.21 5.24 NA Hazy Does not Comply
2. Initial 0.05 BDL 99.9 113 Complies
1 M 0.06 BDL 100.1 113 Complies
2M Hazy Hazy NA Hazy Does not Comply
3. Initial 0.01 BDL 99.5 113 Complies
1 M 0.12 0.08 100.2 113 Complies
3 M Hazy Hazy NA Hazy Does not comply

In another embodiment of the present invention categorized as Packing B condition, wherein the D-Cycloserine dry powder is first packed in a Nylon bag and heat sealed under vacuumized packing condition. The Nylon bag is then placed in an inner LDPE bag along with silica sachet/pouch/bag containing silica calculated as NLT 1 Kg (small pouch/bag of 50g to 250g evenly distributed in LDPE bag) for 25 kg D-Cycloserine dry powder and heat sealed under nitrogen.

The inner LDPE bag is further placed in a Triple laminated aluminum bag along with silica sachet/pouch/bag containing silica calculated as NLT 1 Kg (small pouch/bag of 50g to 250g evenly distributed in TLAB) for 25 kg D-Cycloserine dry powder and heat sealed under nitrogen.

The triple laminated aluminum bag is finally stored in a HDPE/ HM HDPE drum or container along with silica sachet/pouch/bag containing silica calculated as NLT 1 Kg (small pouch/bag of 50g to 250g evenly distributed in HDPE/HM HDPE drum) for 25 kg D-Cycloserine dry powder.

In another embodiment the stability of the D-Cycloserine dry powder of the present invention under Packing B conditions is studied at 25 + 2°C /65 + 5%RH and at 40 + 2°C/75 + 5%RH and the outcome of the study is as provided in the following Table-3 and Table-4, respectively.

Table-3: Stability at 25 + 2°C /65 + 5%RH

S.N Stability condensation
product
(NMT 0.8) Dimer
(NMT 0.2%) Any unspecified impurity
(NMT 0.10%) Assay
(98.5-101.5 %)
SOR
(108-114°) Remarks
1. Initial 0.12 BDL 0.06 99.7 113 Complies
1 M 0.05 BDL 0.05 100.0 113 Complies
2 M 0.05 0.07 BDL 99.6 113 Complies
3 M 0.06 BQL 0.05 99.8 112 Complies
6 M 0.04 BDL BQL 99.9 113 Complies
2. Initial 0.08 0.09 0.05 99.6 112 Complies
1 M 0.04 BQL BDL 100.2 113 Complies
2 M 0.04 0.06 BDL 99.6 113 Complies
3 M 0.04 BDL BDL 100 113 Complies
6 M 0.05 BDL BQL 99.8 112 Complies
3. Initial 0.08 BDL 0.05 99.8 113 Complies
1 M 0.05 BQL BDL 100.3 113 Complies
2 M 0.05 0.06 BQL 99.7 113 Complies
3 M 0.06 BDL BDL 99.8 113 Complies
6 M 0.04 BDL BQL 100 113 Complies
4. Initial 0.04 BDL BDL 99.5 113 Complies
1 M 0.04 BQL BQL 100.1 113 Complies
2 M 0.05 0.08 BQL 99.7 113 Complies
3 M 0.05 BQL BDL 99.3 113 Complies
6 M 0.04 BDL BQL 100 113 Complies

Table-4: Stability at 40 + 2°C/75 + 5%RH

S.N Stability condensation
product
(NMT 0.8) Dimer
(NMT 0.2%) Any unspecified impurity
(NMT 0.10%) Assay
(98.5-101.5 %)
SOR
(108-114°) Remarks
1. Initial 0.12 BDL 0.06 99.7 113 Complies
3 M 1.3 1.51 0.20 Not analyzed Hazy solution Does not Comply
2. Initial 0.08 0.09 0.05 99.6 112 Complies
3 M 2.34 2.57 0.26 Not analyzed Hazy solution Does not Comply
3. Initial 0.08 BDL 0.05 99.8 113 Complies
3 M 4.78 Hazy solution Hazy solution Not analyzed Hazy solution Does not Comply
4. Initial 0.04 BDL BDL 99.5 113 Complies
3 M 3.34 Hazy solution Hazy solution Not analyzed Hazy solution Does not Comply

In a preferred embodiment, Packing B Conditions of the present invention provides 6 months stability at 25 + 2°C.

In yet another embodiment categorized as Packing C Condition, the D-Cycloserine dry powder is first packed in a Nylon bag and heat sealed under vacuumized packing condition. The Nylon bag is then placed in a Triple Laminate Sunlight Barrier bag (TLSB) along with silica sachet/pouch/bag containing silica calculated as NLT 1 Kg (small pouch/bag of 50g to 250g evenly distributed in LDPE bag) for 25 kg D-Cycloserine dry powder and heat sealed under nitrogen.

The TLSB bag is then placed in a QLUB bag along with silica sachet/pouch/bag containing silica calculated as NLT 1 Kg (small pouch/bag of 50g to 250g evenly distributed in TLAB) for 25 kg D-Cycloserine dry powder and heat sealed under nitrogen.

The QLUB bag is finally packed in a HDPE/ HM HDPE drum or container along with silica sachet/pouch/bag containing silica calculated as NLT 1 Kg (small pouch/bag of 50g to 250g evenly distributed in HDPE/HM HDPE drum) for 25 kg D-Cycloserine dry powder.

In another embodiment the stability of the D-Cycloserine dry powder of the present invention under Packing C conditions is studied at 25 + 2°C /65 + 5%RH and at 40 + 2°C/75 + 5%RH and the outcome of the study is as provided in the following Table-5 and Table-6, respectively.

Table-5: Stability at 25 + 2°C /65 + 5%RH

S.N Stability condensation
product
(NMT 0.8) Dimer
(NMT 0.2%) Any unspecified impurity
(NMT 0.10%) Assay
(98.5-101.5 %)
SOR
(108-114°) Remarks
1. Initial 0.08 0.09 0.05 99.6 112 Complies
1 M 0.04 BQL BDL 100.3 112 Complies
2 M 0.04 0.06 BDL 99.7 112 Complies
3 M 0.05 BQL BQL 100 113 Complies
6 M 0.04 BDL BQL 100 113 Complies
2. Initial 0.08 BDL 0.05 99.8 113 Complies
1 M 0.07 BDL BDL 100.1 112 Complies
2 M 0.07 0.06 BQL 99.4 112 Complies
3 M 0.05 BQL BDL 99.6 113 Complies
6 M 0.06 BDL BQL 99.9 113 Complies
3. Initial 0.04 BDL BDL 99.5 113 Complies
1 M 0.06 BQL BQL 100.0 113 Complies
2 M 0.05 0.07 BQL 99.3 113 Complies
3 M 0.05 BQL BQL 99.5 113 Complies
6 M 0.05 BDL BQL 99.4 113 Complies
4. Initial 0.01 BDL BQL 99.4 113 Complies
1 M 0.05 BDL BQL 99.9 112 Complies
2 M 0.04 0.06 BQL 99.3 112 Complies
3 M 0.04 BQL BQL 99.7 111 Complies
6 M 0.04 BQL BQL 99.6 113 Complies

Table-6: Stability at 40 + 2°C/75 + 5%RH

S.N Stability condensation
product
(NMT 0.8) Dimer
(NMT 0.2%) Any unspecified impurity
(NMT 0.10%) Assay
(98.5-101.5 %) SOR
(108-114°) Remarks
1. Initial 0.08 0.09 0.05 99.6 112 Complies
3 M 0.04 BQL BQL 99.5 112 Complies
6 M 0.04 BDL BQL 100 112 Complies
2. Initial 0.08 BDL 0.05 99.8 113 Complies
3 M 0.05 BQL BQL 99.4 112 Complies
6 M 0.07 BQL BDL 99.1 113 Complies
3. Initial 0.04 BDL BDL 99.5 113 Complies
3 M 0.05 BQL BQL 99.3 113 Complies
6 M 0.07 BQL BDL 99.0 112 Complies
4. Initial 0.01 BDL BQL 99.4 113 Complies
3 M 0.04 BDL BQL 99.6 111 Complies
6 M 0.05 BQL BDL 99.9 113 Complies

In a preferred embodiment, the Packing C conditions of the present invention provide 6 months stability at 40°C.

The D-Cycloserine dry powder of the present invention is prepared by following Example-1 and Example-2.

In one more embodiment the present invention also provides a pharmaceutical composition comprising the storage stable D-Cycloserine of the present invention along with one or more pharmaceutically acceptable carriers, excipients, or diluents.

The storage stable D-Cycloserine of the present invention is used for the treatment of active pulmonary and extra pulmonary tuberculosis.

The storage stable D-Cycloserine of the present invention is used in preparing pharmaceutical composition for the treatment of active pulmonary and extra pulmonary tuberculosis. Such pharmaceutical compositions are prepared by the methods known in the literature.

The present invention is further illustrated with the following non-limiting examples.

Example-1:
Preparation of crude D-Cycloserine
To a chilled solution of hydroxylamine hydrochloride (138 gm; 1.19 Moles) in 2100 mL methanol, caustic soda lye (287 gm net basis, 7.18 Moles) was added at -5 to -15°C. Thereafter, pre-chilled solution of D-2-amino 3-chloro propionic acid methyl ester HCl (300 gm, 1.72 moles) in 738 mL of aqueous methanol was added slowly at -40 to -50°C and stirred for 1.5 hr. The temperature was raised to 0°C and the pH was adjusted to 11.0 to 11.7 with ~43 mL of acetic acid and maintained for 1.5 hours at 10 to15°C and thereafter at 25-30°C for 1.5 hr maintaining pH of 11.0 to 11.7 by adding caustic soda lye solution. Upon completion of reaction, as monitored by HPLC, the reaction mass was cooled to 0 to -10°C, filtered to remove sodium hydrochloride and washed with 300 mL methanol. The pH of the filtrate obtained is adjusted to pH to 6.3-6.7 with ~150 mL Acetic acid at 0 to -10°C to afford crude wet D-Cycloserine.

Example-2:
Purification of crude D-Cycloserine to Cycloserine

110 gm of crude wet Cycloserine (on dry basis) was dissolved in 550 mL, 6-8% dilute ammonia solution at ~ 0°C. Thereafter pre-chilled 1100 ml Dysol (denatured ethanol in IPA) was added and the reaction mass was filtered through celite followed by washing of celite bed with 220 ml of Dysol. The pH of filtrate is adjusted to 6.3-6.7 with ~195 ml of acetic acid at about 0°C to afford wet product. The wet cake of D-Cycloserine was leached with a mixture of 352 mL of Dysol and 88 mL water at 10-15°C, filtered,
washed with 352 mL Dysol and dried under vacuum to get purified D-Cycloserine dry powder.
,CLAIMS:
1. A storage of stable D-Cycloserine.

2. The storage of stable D-Cycloserine according to claim-1 provides an efficient packing system.

3. The storage of stable D-Cycloserine according to claim-1, where an efficient packing system involves ‘packing condition A’, ‘packing condition B’ or ‘packing condition C’.

4. The storage of stable D-Cycloserine according to claim-1 where Packing A condition D-Cycloserine dry powder is first packed in low density polythene bag (LDPE) bag and heat sealed under vacuumized packing condition; this bag is then placed in another inner LDPE bag and twist and tied with plastic fastener; it is then placed in Triple laminated aluminum bag along with silica sachet/pouch/bag containing silica calculated as NLT 1 Kg (small pouch/bag of 50g to 250g evenly distributed in TLAB) for 25 kg dry Cycloserine packed and heat sealed under nitrogen; this bag is then kept in high density polyethylene (HDPE)/ high molecular-high density polyethylene (HM- HDPE) drum or container.

5. The storage of stable D-Cycloserine according to claim-1, where Packing B condition involves D-Cycloserine dry powder is first packed in Nylon bag and heat sealed under vacuumized packing condition; this bag is then placed in another inner LDPE bag along with silica sachet/pouch/bag containing silica calculated as NLT 1 Kg (small pouch/bag of 50g to 250g evenly distributed in LDPE bag) for 25 kg dry and heat sealed under nitrogen; it is then placed in Triple laminated aluminum bag along with silica sachet/pouch/bag containing silica calculated as NLT 1 Kg (small pouch/bag of 50g to 250g evenly distributed in TLAB) for 25 kg dry D-Cycloserine packed and heat sealed under nitrogen; this triple laminated aluminum bag is then kept in HDPE/ HM HDPE drum or container as per customer specification along with silica sachet/pouch/bag containing silica calculated as NLT 1 Kg (small pouch/bag of 50g to 250g evenly distributed in HDPE/HM HDPE drum) for 25 kg dry D-Cycloserine powder.

6. The storage of stable D-Cycloserine according to claim-1, where Packing C condition involves the D-Cycloserine dry powder is first packed in Nylon bag and heat sealed under vacuumized packing condition; this Nylon bag is then placed in TLSB bag along with silica sachet/pouch/bag containing silica calculated as NLT 1 Kg (small pouch/bag of 50g to 250g evenly distributed in LDPE bag) for 25 kg dry and heat sealed under nitrogen; it is then placed in QLUB bag along with silica sachet/pouch/bag containing silica calculated as NLT 1 Kg (small pouch/bag of 50g to 250g evenly distributed in TLAB) for 25 kg dry D-Cycloserine packed and heat sealed under nitrogen; the QLUB bag is then kept in HDPE/ HM HDPE drum or container along with silica sachet/pouch/bag containing silica calculated as NLT 1 Kg (small pouch/bag of 50g to 250g evenly distributed in HDPE/HM HDPE drum) for 25 kg dry D-Cycloserine powder.

7. The storage of stable D-Cycloserine according to claim-1, wherein the efficient packing system maintains the dimer impurity to not more than 0.2 %.

8. The storage of stable D-Cycloserine according to claim-1, where the storage conditions of API, that is, Packing C conditions at which stability complies at accelerated conditions (40 + 2°C/75 + 5%RH) for 6 months.

9. The storage of stable D-Cycloserine according to claim-1, wherein the efficient packing system maintains potency.

10. The storage of stable D-Cycloserine according to claim-1 involves multiple packing, inert atmosphere under vacuum optionally in presence of desiccants.