Scaled-up synthesis of lomustine under continuous flow conditions

Abstract

To provide a scaled-up synthesis of lomustine under continuous flow conditions.SOLUTION: The present disclosure provides processes and apparatuses for the scaled-up manufacture of lomustine via continuous flow manufacture. Such continuous flow processes may optionally include the crystallization of lomustine and the apparatuses may optionally include crystallization apparatuses / reactors in either batch or continuous flow design. In one aspect of the disclosure, there is provided a process for making lomustine comprising: treating solutions of 2-chloroethylisocyanate with a solution of cyclohexylamine with continuous-flow pumps in a gram-flow reactor to form a combined solution; adding deionized water with a continuous flow-pump to the combined solution to form a liquid-organic phase solution; extracting the organic phase from the solution; and treating with a solution of t-butyl nitrite with a continuous flow pump in a gram flow reactor to form lomustine.SELECTED DRAWING: None

Description

[Technical Field]

[0001] government support This invention was made with government support under grants CA023168 awarded by the National Institutes of Health, W911NF-16-2-0020 awarded by the Defense Advanced Research Projects Agency, and FD-U-006738 awarded by the Food and Drug Administration. The government has certain rights in this invention.

[0002] FIELD OF THE INVENTION The present disclosure provides a novel method for synthesizing the drug lomustine in scalable sizes under continuous flow conditions. [Background technology]

[0003] background Lomustine, a widely used anticancer drug, is a highly lipophilic alkylating agent that generates chloroethyl carbonium ions and carbamylated intermediates in vivo. These electrophilic compounds attack nucleophilic sites on DNA to form alkylation products. While other anticancer drugs, such as mitomycin C, streptonigrin, bleomycin, and anthracyclines, require bioactivation to react with their cellular targets, lomustine does not require preactivation. The most reactive N-terminal residue of guanine 7 Unlike alkylating agents that form adducts at the O-position, chloroethylated compounds such as lomustine 6 This leads to the formation of adducts with ATP, resulting in interstrand DNA crosslinks. If DNA repair does not occur, these crosslinks can cause double-strand breaks during DNA replication and ultimately cell death via apoptosis.

[0004] Lomustine, 1-(2-chloroethyl)-3-cyclohexyl-1-nitroso-urea (trade names: CCNU, CeeNU, Gleostine), is used as an oral antineoplastic agent administered every six weeks. It was first evaluated in clinical trials in the late 1960s and approved by the U.S. FDA in 1976 for primary and metastatic brain tumors and Hodgkin's lymphoma. Bristol-Myers Squibb initially held the patent for this drug under the trade name CeeNU. In 2014, Next Source Biotechnology LLC (NSB) was approved by the FDA to rebrand lomustine under the trade name Gleostine. The average wholesale price of a single dose of rebranded Gleostine is $1,645.68, compared with $203.38 for the generic formulation. The large price discrepancy (over 800%) between Gleostine and generic formulations has created patient access issues and a need for lower-cost lomustine.

[0005] Continuous flow synthesis has been reported as an efficient methodology and has been investigated in both industrial and academic research laboratories for the past few decades. Compared to traditional batch synthesis processes, flow reactors offer better control over reaction conditions and selectivity due to rapid mixing and precise control of reaction parameters such as temperature, stoichiometry, pressure, and residence time. Enhanced heat and mass transfer capabilities also provide safer and more environmentally friendly operating conditions. In general, these aspects of continuous flow synthesis contribute to improved chemical reaction efficiency and shorter reaction times, enabling process intensification and easier scale-up with improved quality and consistency in production. Motivated by these factors, continuous flow synthesis of active pharmaceutical ingredients has recently become more attractive; however, efficiently executing nested multistep reactions remains challenging due to challenges arising from workup requirements, solvent switches, and flow rate differences. Furthermore, optimization of continuous flow conditions and analysis requires significant investments in time and materials. In U.S. Patent Application Publication Nos. 62 / 746,045 and 16 / 654,103, now published as U.S. Patent Application Publication Nos. 20200115330A1, the inventors disclose novel methods for producing lomustine under continuous flow conditions. Herein, the inventors further describe novel methods for producing lomustine under continuous flow conditions that improve upon the processes disclosed in U.S. Patent Application Publication Nos. 62 / 746,045 and 16 / 654,103, now published as U.S. Patent Application Publication Nos. 20200115330A1, the contents of which are part of this disclosure under Appendix A and further incorporated herein by reference in their entireties. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] U.S. Patent Application Publication No. 20200115330A1 Summary of the Invention [Means for solving the problem]

[0007] overview In one aspect of the disclosure, a method of making lomustine is provided, comprising treating a solution of 2-chloroethyl isocyanate with a solution of cyclohexylamine in a gram-flow reactor using a continuous flow pump to form a mixed solution, adding deionized water to the mixed solution using a continuous flow pump to form a liquid-organic phase solution, extracting the organic phase from the solution, and treating with a solution of t-butyl nitrite in a gram-flow reactor using a continuous flow pump to form lomustine.

[0008] In another aspect of the present disclosure, there is provided an apparatus substantially similar to that of FIG.

[0009] In a further aspect of the present disclosure, there is provided an apparatus substantially similar to that of FIG. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 shows a diagram of making and crystallizing lomustine. [Figure 2] FIG. 2 shows a diagram of making and crystallizing lomustine. [Figure 3] FIG. 3 shows a diagram of making and crystallizing lomustine. DETAILED DESCRIPTION OF THE INVENTION

[0011] Detailed Description While the concepts of the present disclosure have been illustrated and described in detail in the drawings and description herein, the results in the drawings and their description are to be regarded as illustrative and not as limiting in character; it being understood that only exemplary embodiments have been shown and described, and that all changes and modifications that come within the spirit of the present disclosure are desired to be protected.

[0012] Unless otherwise defined, scientific and technical nomenclature has the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains.

[0013] Continuous flow manufacturing at large scale presents particular challenges. It is important to identify solvents in which the reactants are sufficiently soluble so that throughput is maximized without precipitation, which can force shutdowns. Another challenge in continuous flow manufacturing is product purity. Crystallization is usually the best method for achieving high purity, but it is more difficult to achieve continuously, and contamination in the mother liquor must be low to enable such crystallization.

[0014] With respect to lomustine, to produce enough lomustine to meet commercial needs, a flow reactor should be capable of producing 250 grams / day or more. The synthesis shown in Appendix A has been optimized to provide only about 110 mg / hour, which, when run 24 hours per day, represents only about 1% of the scale-up requirement. The disclosure herein describes a process where 250 grams / day is achievable. Furthermore, the current process utilizes the ability to crystallize lomustine as needed, thus increasing purity and avoiding the need for additional handling and transportation to a facility or reactor for further crystallization.

[0015] Figure 1 illustrates a scale-up embodiment of the present disclosure in which both batch and continuous crystallization settings are disclosed, Figure 2 illustrates a scale-up embodiment with batch crystallization, and Figure 3 illustrates a scale-up embodiment with continuous crystallization.

[0016] To create a solution for preparing lomustine, a suitable solvent for 2-chloroethyl isocyanate and cyclohexylamine is prepared. Such solvents often have a high boiling point and are immiscible with water. An example of such a suitable solvent is 2-methyltetrahydrofuran. The solvent for 2-chloroethyl isocyanate does not need to be the same as the solvent for cyclohexylamine, but in many embodiments, the solvents are the same.

[0017] The 2-chloroethyl isocyanate solution and the cyclohexylamine solution are combined to form the intermediate 2-chloroethylcyclohexylurea, which then flows into a reactor. The reactor can be, for example, a continuous plug flow reactor. An example of such a reactor is the "GramFlow" reactor manufactured by Chemtrix, Ltd. The GramFlow reactor has highly enhanced mixing due to its zigzag flow field structural design and its integrated heat exchanger plate, which allows for excellent heat transfer. The GramFlow reactor has two inlets and one outlet and accommodates 1 / 16-inch or 1 / 8-inch tubing using 1 / 4-28 flat-bottom flangeless fittings. The reactor has a volume of 1.6 mL, a temperature range of -20 to 150°C, and can withstand operating pressures of up to 20 bar. All wetted materials are made of highly chemically resistant materials such as borosilicate glass, polytetrafluoroethylene, and perfluoroelastomers.

[0018] The mixed solution can be further processed in a coiled flow reactor or a second GramFlow reactor. A coiled flow reactor is a reactor in which the reagents are subjected to non-laminar flow, thereby improving mixing and reaction uniformity in the flow field. To help identify the completion and purity of the process reaction, one or more analytical instruments can be used to monitor the preparation of lomustine during the process. Examples of such instruments include Raman spectroscopy and UV-visible spectroscopy.

[0019] The reaction to prepare lomustine involves combining an aqueous phase and an organic phase during the reaction process. The aqueous phase can be introduced by adding t-butyl nitrite in water. Lomustine exhibits higher solubility in organic solvents (e.g., 2-methyltetrahydrofuran) than in water, and extraction, in which the aqueous phase is discarded or reused, increases the purity of lomustine in the organic phase. Repeated extractions of the aqueous phase can be used to increase the yield of lomustine provided.

[0020] A continuous flow of the reaction product and lomustine in solution is maintained by a pump. Traditionally, syringes have been used to maintain the flow, but this is not well suited for scale-up manufacturing. Continuous flow pumps are often positive displacement units. Examples of such pumps use four or more pistons to provide a continuous flow with minimal flow oscillations.

[0021] As shown in Figure 1, batch or continuous crystallization can be used as needed to prepare crystalline lomustine. In the batch crystallization process shown in Figure 2, an anti-solvent can be pumped into a batch crystallization reactor and combined with a solution of lomustine. The resulting mixture is then transferred to equipment for filtration or drying, thereby isolating the crystalline lomustine. Analytical equipment, represented by "PAT3," can be added to monitor various reaction parameters, such as purity or crystallization.

[0022] In an alternative crystallization process, lomustine crystallization occurs via continuous crystallization as opposed to batch crystallization, as shown in Figure 3. In this method, a solution of lomustine is transferred to a continuous evaporation column where it is concentrated and then pumped to a continuous crystallizer, from which it is filtered and dried to obtain lomustine crystals.

[0023] Additionally, any of the embodiments described in the list of sections below are considered part of the present invention. Item 1. A method for producing lomustine is provided, the method comprising: (i) treating a solution of 2-chloroethyl isocyanate with a solution of cyclohexylamine in a Gram-Flow flow reactor using a continuous flow pump to form a mixed solution; (ii) adding deionized water to the mixed solution using a continuous flow pump to form a liquid-organic phase solution; (iii) extracting the organic phase from the solution; (iv) treating the organic phase with a solution of t-butyl nitrite in a flow reactor using a continuous flow pump to form a lomustine solution; A method comprising: Item 2. The method according to Item 1, wherein the mixed solution is pumped into a coiled flow reactor. Item 3. The method according to Item 1 or 2, wherein the organic phase in step (iv) is pumped into a coiled flow reactor. Clause 4. The method of clauses 1, 2, or 3, wherein the method is monitored by one or more analytical instruments. Clause 5. The method of clause 4, wherein at least one of the one or more analytical instruments is a spectrometer. Item 6. The method of item 5, wherein the spectrometer is a Raman spectrometer. Item 7. The method according to Item 5, wherein the spectrometer is an ultraviolet-visible spectrometer. Item 8. The method of items 1 to 7, further comprising further extracting the organic phase with water to further purify the lomustine solution. Item 9. The method of item 8, wherein the water is deionized water and is delivered via a pump. Item 10. The method according to items 8 to 9, wherein extraction occurs after step (iv). Item 11. The method according to any one of Items 1 to 10, further comprising crystallizing lomustine. Item 12. The method of item 11, wherein the crystallization of lomustine occurs through batch crystallization. Item 13. The method of item 12, wherein the lomustine solution is combined with the antisolvent via a pump. Item 14. The method of item 13, wherein the anti-solvent is combined with the lomustine solution in a batch crystallizer. Item 15. The method according to Item 14, wherein the solvent is removed to produce crystals of lomustine. Item 16. The method of item 14, wherein the solvent is removed by drying. Clause 17. The method of clauses 11 to 16, wherein the method is monitored by one or more analytical instruments. Item 18. The method of item 17, wherein at least one analytical instrument is a Raman spectrometer. Item 19. The method according to Item 17, wherein at least one analytical instrument is an X-ray powder diffractometer. Item 20. The method of item 11, wherein the crystallization of lomustine occurs through continuous crystallization. Item 21. The method of item 20, wherein the lomustine solution is pumped through a continuous evaporation column to form a concentrated solution of lomustine. Item 22. The method of item 21, wherein a concentrated solution of lomustine is combined with an antisolvent and pumped into a continuous crystallizer. Item 23. The method according to Item 22, wherein lomustine is filtered in a continuous crystallizer. Item 24. The method of items 23 and 24, wherein lomustine is dried to produce lomustine crystals. Item 25. The method of any one of items 1 to 24, wherein the solution of cyclohexylamine and the solution of 2-chloroethyl isocyanate are dissolved in a solvent that is immiscible with water. Item 26. The method according to Item 25, wherein the solvent is 2-methyltetrahydrofuran. Item 27. The method according to any one of items 1 to 6, wherein the t-butyl nitrite is in a water-soluble solvent. Item 28. The method according to Item 27, wherein the solvent is THF. Item 29. The method of any one of items 1 to 28, wherein at least one flow reactor is ceramic. Item 30. The method according to Item 29, wherein the ceramic is SiC. Item 31. Substantially the same apparatus as in FIG. 2. Item 32. Substantially the same apparatus as in FIG. 3. Item 33. The method according to any one of Items 2 to 30, wherein the mixed solution contains 2-chloroethylcyclohexylurea. Item 34. The method according to Item 33, wherein the organic phase contains 2-chloroethylcyclohexylurea.

[0024] Hypothetical Example Disclosed herein are embodiments within the scope of the present disclosure.

[0025] pump All liquid feeds to the reactor are managed using a MilliGAT MG-2-CER-XT FSPS-6 pump system (Global FIA, Fox Island, Washington). These MilliGAT pumps are positive displacement units that utilize four cooperating pistons to deliver continuous flow with minimal flow oscillation. They also offer high chemical resistance, as all wetted materials are made from PTFE and ceramic zirconia. This model has a flow rate range of 0.0024 to 30 mL / min and a maximum operating pressure of 200 PSI. The pump station features PID temperature control, allowing direct control of heating or cooling units during the process using the touch tablet FLUMI interface or via a customized Labview user interface.

[0026] Heated Coiled Tubular Reactor A customized heated coiled tube reactor was used, using polytetrafluoroethylene (PTFE) tubing (WW Grainger Inc., USA) with an inner diameter of 1 / 16 inch and an outer diameter of 1 / 8 inch. The tubing itself was wrapped around a carved steel central core containing a heating element controlled by an Omega CNi series PID temperature controller. The core with the attached coiled tubing was then clamped between two steel shells. The core and shells were then placed on an enclosure containing calcium silicate insulation panels to stabilize and maintain the reactor's set temperature. The reactor had one inlet and one outlet; therefore, a T-mixer or cross-mixer was used to combine multiple solutions at the reactor inlet. After assembling the reactor, flat-bottom flangeless fittings and connections (1 / 4-28) were used to connect the tubing to the T-mixer or cross-mixer. The volume of this reactor was approximately 11 mL (tubing length = 5.56 cm). The maximum operating temperature of the reactor is 200°C, and the maximum operating pressure depends on the tubing used in the reactor (approximately 290 PSI for 1 / 8 inch PTFE tubing at 22.8°C).

[0027] CFI Reactor / Mixer The second reactor used is a custom-made coiled flow inverter (CFI) reactor. This reactor also uses 1 / 8-inch PTFE tubing (WW Grainger, USA). The tubing is tightly wrapped around four standard 1 / 4-inch 90° copper fittings, allowing for the construction of a square reactor. The CFI reactor provides enhanced mixing, mass transfer, and heat transfer compared to simple coiled reactors. Each reactor had a volume of 8 mL (tubing length = 405 cm). Multiple 8 mL CFI reactors were constructed to allow for easy changes in reaction volume or residence time by connecting the desired number of CFI units in series using 1 / 4-28 flat-bottom flangeless fittings and connectors.

[0028] GramFlow Reactor / Mixer The GramFlow reactor (Chemtrix, Ltd., The Netherlands) is a continuous plug flow reactor with highly enhanced mixing due to its zigzag flow field structural design and its integrated heat exchanger plate, which allows for excellent heat transfer. The GramFlow reactor has two inlets and one outlet and accommodates 1 / 16-inch or 1 / 8-inch tubing using 1 / 4-28 flat-bottom flangeless fittings. The reactor has a volume of 1.6 mL, a temperature range of -20 to 150°C, and can withstand operating pressures of up to 20 bar. All wetted materials are made of highly chemically resistant materials such as borosilicate glass, PTFE, and FFKM.

[0029] liquid-liquid separator Two SEP-10 units (Zaiput Flow Technologies, USA) were used for liquid-liquid separation. The SEP-10 units utilize a porous hydrophobic PTFE membrane (OB-400) to allow the organic phase (wet phase) to flow through the membrane, while the aqueous phase passes through the membrane and exits the separator. The SEP-10 units have an internal pressure controller that maintains a pressure differential across the membrane to allow for better separation of the two phases. The separation efficiency of this unit depends on several factors, including but not limited to, the membrane material and pore size, the total inlet flow rate, the separation temperature, and the interfacial tension between the organic and aqueous phases.

[0030] Synthesis of lomustine Solutions of cyclohexylamine and 2-chloroethyl isocyanate were prepared separately in anhydrous 2-methyltetrahydrofuran under a dry N2 atmosphere. The solutions were added to two amber GL45 glass bottles to protect them from light (2-chloroethyl isocyanate is light-sensitive). Throughout the process, all transfer lines for 2-chloroethyl isocyanate (PTFE tubing with an inner diameter of 1 / 16 inch and an outer diameter of 1 / 8 inch) were covered with aluminum tape for light protection. After installing a 0.2 μm PTFE inlet filter, the transfer lines were routed through the GL45 solvent delivery cap, which was then connected to the inlet of the milliGAT pump array before being placed into the charged amber starting material bottle. The solvent delivery cap has two ports, one for the transfer line and the other for the N2 flow, so that the bottle is kept under inert conditions as the solvent is dispensed. Following the pump outlet, a T-relief valve assembly and subsequent check valves were installed at each pump outlet, and the transfer piping was then connected to a T-mixer preceding the heated coiled tubing reactor. The T-relief valve assembly and check valves were used to prevent overpressurization of the process and avoid backflow in the piping. The reactor temperature was set to approximately 50°C, with a residence time of 1-3 minutes. The outlet of the heated coiled tubing reactor, containing the 2-chloroethylcyclohexylurea intermediate solution resulting from the reaction of cyclohexylamine and 2-chloroethyl isocyanate, was connected to a T-mixer, where deionized water was added to extract water-soluble impurities while retaining the 2-chloroethylcyclohexylurea intermediate in the organic phase before the mixture entered the Zaiput membrane separator. The organic phase outlet of the separator was connected to the next reaction step, while the other outlet transported the aqueous extract phase to a waste container. A solution of tert-butyl nitrite was prepared in anhydrous tetrahydrofuran under dry N2, placed in an amber GL45 glass bottle, and connected to the pump following the same procedure as above. Using another MilliGAT pump, tert-butyl nitrite is added through a T-mixer to the organic phase containing the 2-chloroethylcyclohexylurea intermediate. The reaction mixture is then passed through a series of 13 CFI reactors at 20°C for a total residence time of 10 minutes to produce lomustine.The outlet of the CFI reactor train containing the lomustine product is connected to a T-mixer where deionized water is added to extract water-soluble impurities. After flowing through a Zaiput membrane separator, the organic phase is retained for further purification of the lomustine product via crystallization, while the other outlet transfers the aqueous phase to a waste container. The present invention provides, for example, the following items. (Item 1) A method of making lomustine is provided, the method comprising: (i) treating a solution of 2-chloroethyl isocyanate with a solution of cyclohexylamine in a flow reactor using a continuous flow pump to form a mixed solution; (ii) adding deionized water to the mixed solution using a continuous flow pump to form a liquid-organic phase solution; (iii) extracting the organic phase from the solution; (iv) treating the organic phase with a solution of t-butyl nitrite in a flow reactor using a continuous flow pump to form a lomustine solution; A method comprising: (Item 2) Item 10. The method according to item 1, wherein the mixed solution is pumped into a coiled flow reactor. (Item 3) 3. The process according to claim 1 or 2, wherein the organic phase of step (iv) is pumped to a coiled flow reactor. (Item 4) 4. The method of claim 1, 2, or 3, wherein the method is monitored by one or more analytical instruments. (Item 5) 5. The method of claim 4, wherein at least one of the one or more analytical instruments is a spectrometer. (Item 6) 6. The method of claim 5, wherein the spectrometer is a Raman spectrometer. (Item 7) Item 6. The method of item 5, wherein the spectrometer is a UV-visible spectrometer. (Item 8) 8. The method of claim 1, further comprising further extracting the organic phase with water to further purify the lomustine solution. (Item 9) 9. The method of claim 8, wherein the water is deionized water and is delivered via a pump. (Item 10) 10. The method according to items 8 to 9, wherein the extraction occurs after step (iv). (Item 11) 11. The method of items 1 to 10, further comprising crystallizing lomustine. (Item 12) 12. The method of claim 11, wherein said crystallization of lomustine occurs through batch crystallization. (Item 13) 13. The method of claim 12, wherein the lomustine solution is combined with the antisolvent via a pump. (Item 14) 14. The method of claim 13, wherein the anti-solvent is combined with the lomustine solution in a batch crystallizer. (Item 15) 15. The method of claim 14, wherein the solvent is removed to produce crystals of lomustine. (Item 16) 15. The method of claim 14, wherein the solvent is removed by drying. (Item 17) 12. The method of claim 11, wherein the method is monitored by one or more analytical instruments. (Item 18) Item 18. The method according to item 17, wherein at least one analytical instrument is a Raman spectrometer. (Item 19) Item 18. The method according to item 17, wherein at least one analytical instrument is an X-ray powder diffractometer. (Item 20) 12. The method of claim 11, wherein said crystallization of lomustine occurs through continuous crystallization.

Claims

[Claim 1] The invention described in the present specification.

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