EC50: 0.1 nM (FKBP, in HT1080 cells)[1] Fas receptor[1]
FKBP12 (Fv) (modified human FKBP12 with Phe36Val substitution). AP1903 binds to the modified FKBP12 domain (Fv) with high affinity, inducing homodimerization. This dimerization brings together two Fv domains, which can be used to activate signaling pathways such as Fas-mediated apoptosis or caspase-9 activation. The compound has 1000-fold lower affinity for wild-type FKBP12, ensuring specificity for the modified Fv domain.

Rimiducid (AP1903) causes significant and dose-dependent apoptosis of modified cells in culture, with an EC50 of around 0.1 nM [1]. Maximum killing occurs in the presence of 3 to 10 nM Rimiducid (AP1903), with an IC50 of around 0.2 nM. LV'VFas-transduced T cells (upper panel) with high levels of CD25 were removed with an efficiency of 66%±7.5% (n=10). After CD25 expression recovered to baseline levels, Rimiducid therapy resulted in 63%±4.7% (n=9) cell death [2].
AP1903 demonstrates potent homodimerizing activity in vitro by cross-linking FKBP domains. It binds specifically to the modified FKBP12 (Fv) domain with high affinity. The compound's ability to induce dimerization has been characterized in various biochemical and cell-based assays. It is commonly used in research applications involving chemically induced dimerization (CID) systems.

Serum human growth hormone levels are reduced in a dosage-dependent manner by fumiducid (AP1903; iv, 0.01, 0.1, 1, 10, and 100 mg/kg); the half-maximum efficacious dose is 0.4 ± 0.1 mg/kg [1].
In vivo, AP1903 is used to induce apoptosis in cells expressing the modified FKBP12 domain and a caspase-9 fusion protein. When administered, the compound dimerizes the caspase-9 suicide switch, rapidly inducing apoptosis in targeted cells. This system is used in cell therapy and gene therapy applications to eliminate unwanted cells. The compound has been studied in various animal models.

In vitro binding assays for AP1903 typically involve surface plasmon resonance or fluorescence polarization to measure binding affinity to FKBP12 (Fv) domains. The compound is incubated with purified Fv protein, and binding is detected using labeled probes. Competition assays may be performed to determine specificity. The compound's ability to induce dimerization can be assessed using size exclusion chromatography or analytical ultracentrifugation.

Cloned HT1080 cell lines (ATCC CCL-121) retrovirally transduced with Fas constructs are prepared. Cell viability after overnight incubation with Rimiducid (0.01 nM, 0.1 nM, 1 nM, 10 nM, 100 nM, 1000 nM) is measured by Alamar Blue assay[1]. For annexin V assays, sorted LV′VFas-transduced T cells (2×106 cells/mL) are incubated with 10 nM Rimiducid. At the indicated time, an aliquot of 2×105 cells is taken, stained with annexin V-fluorescein isothiocyanate, and analyzed by flow cytometry[2].

In vivo animal studies for AP1903 are conducted in mice or other species engrafted with cells expressing the inducible system. The compound is typically administered intraperitoneally or intravenously at doses ranging from 0.1-10 mg/kg. Apoptosis of targeted cells is assessed by measuring cell death, tumor regression, or other relevant endpoints. Dosing regimens vary depending on the experimental design and the specific application.

AP1903 is a lipid-permeable compound with a molecular weight of 1411.63. It is typically stored lyophilized at -20°C, where it is stable for up to 36 months. In solution, it should be stored at -20°C and used within 3 months to prevent loss of potency. The compound is soluble in organic solvents such as DMSO. Detailed pharmacokinetic parameters are not extensively documented in publicly available sources.

AP1903 is generally well-tolerated at research-relevant doses. However, comprehensive toxicological data are limited. The compound is intended for research use only and is not approved for human therapeutic applications. Standard laboratory safety precautions should be taken when handling the compound. It should be stored under recommended conditions to maintain stability.

[1]. Redesigning an FKBP-ligand interface to generate chemical dimerizers with novel specificity. Proc Natl Acad Sci U S A. 1998 Sep 1;95(18):10437-42.

[2]. A Fas-based suicide switch in human T cells for the treatment of graft-versus-host disease. Blood. 2001 Mar 1;97(5):1249-57.

Rimiducid is a lipid-soluble tacrolimus analog and a protein dimerizing agent. It is designed to overcome the limitations of current cell immunotherapies used to treat cancer and other blood disorders by enhancing control over the activity and function of immune cells. When administered via chemically induced dimerization (CID) technology, Rimiducid binds to and dimers a switch protein, triggering a downstream signaling cascade. The combination of Rimiducid with immunotherapy is currently being investigated to enhance therapeutic efficacy. Rimiducid is a lipid-soluble tacrolimus analog with homodimerizing activity. The dimerizing agent AP1903 can homodimerize an analog of the human protein FKBP12 (Fv) containing a one-amino acid substitution (Phe36Val), thus reducing the binding affinity of AP1903 to wild-type FKBP12 by 1000-fold. This drug is used to homodimerize the drug-binding domain containing the Fv fragment of genetically engineered receptors (such as the iCD40 receptor of the autologous dendritic cell vaccine BP-GMAX-CD1), thereby activating the receptor.

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Drug Indications
It has been investigated for the treatment of bone marrow transplantation and graft-versus-host disease.
Treatment of Graft-versus-Host Disease
Mechanism of Action
Rimiducid binds to a drug-binding domain derived from the human FK506 binding protein, which is located on a modified inducible caspase-9. This binding leads to caspase-9 dimerization and subsequent activation. This system is designed as a “safety switch” in CAR-T cell therapy for hematologic malignancies. The retroviral vector used to produce these modified cells preferentially integrates this gene near a promoter associated with T cell activation. This results in increased expression levels of the modified inducible caspase-9 product in activated T cells. In effect, this allows rimiducid to specifically target these activated T cells, thereby reducing the number of circulating cells by more than 90% in cases of graft-versus-host disease. This specificity does not affect allogeneic reactive T cells and allows for the successful reconstruction of the transplanted immune system using these cells. [24753538] Furthermore, these allogeneic reactive cells remain sensitive to rimiducid.

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Pharmacodynamics
Rimiducid is used to activate inducible caspase-9 produced by a modified gene contained in certain CAR-T cell therapies. This activation rapidly induces apoptosis in activated modified T cells and alleviates the signs and symptoms of graft-versus-host disease within 24 hours.
AP1903 (Rimiducid) is a dimerizer agent that cross-links FKBP domains, inducing apoptosis through Fas signaling or caspase-9 activation. It binds specifically to the modified FKBP12 (Fv) domain with 1000-fold higher affinity than wild-type FKBP12. The compound is used in research applications involving chemically induced dimerization and cell ablation. It is not approved for clinical use and is available only for research purposes.

C78H98N4O20

1411.63

1410.677

195514-63-7

16135625

White to light yellow solid powder

1.2±0.1 g/cm3

1307.5±65.0 °C at 760 mmHg

744.5±34.3 °C

0.0±0.3 mmHg at 25°C

1.566

10.39

2

20

39

102

2330

6

CC[C@@H](C1=CC(=C(C(=C1)OC)OC)OC)C(=O)N2CCCC[C@H]2C(=O)O[C@H](CCC3=CC(=C(C=C3)OC)OC)C4=CC(=CC=C4)OCC(=O)NCCNC(=O)COC5=CC=CC(=C5)[C@@H](CCC6=CC(=C(C=C6)OC)OC)OC(=O)[C@@H]7CCCCN7C(=O)[C@@H](CC)C8=CC(=C(C(=C8)OC)OC)OC

GQLCLPLEEOUJQC-WFMNNBDOSA-N

InChI=1S/C78H98N4O20/c1-13-57(53-43-67(93-7)73(97-11)68(44-53)94-8)75(85)81-37-17-15-25-59(81)77(87)101-61(31-27-49-29-33-63(89-3)65(39-49)91-5)51-21-19-23-55(41-51)99-47-71(83)79-35-36-80-72(84)48-100-56-24-20-22-52(42-56)62(32-28-50-30-34-64(90-4)66(40-50)92-6)102-78(88)60-26-16-18-38-82(60)76(86)58(14-2)54-45-69(95-9)74(98-12)70(46-54)96-10/h19-24,29-30,33-34,39-46,57-62H,13-18,25-28,31-32,35-38,47-48H2,1-12H3,(H,79,83)(H,80,84)/t57-,58-,59+,60+,61+,62+/m0/s1

(S,2R,2'R)-(1R,1'R)-((((ethane-1,2-diylbis(azanediyl))bis(2-oxoethane-2,1-diyl))bis(oxy))bis(3,1-phenylene))bis(3-(3,4-dimethoxyphenyl)propane-1,1-diyl) bis(1-((S)-2-(3,4,5-trimethoxyphenyl)butanoyl)piperidine-2-carboxylate)

AP-1903 Rimiducid AP 1903 AP1903

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Note: This product is not stable in solution, please use freshly prepared working solution for optimal results.

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

DMSO : ~100 mg/mL (~70.84 mM)

Solubility in Formulation 1: ≥ 2.5 mg/mL (1.77 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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Solubility in Formulation 2: 2 mg/mL (1.42 mM) in 2% DMSO 98% Corn Oil (add these co-solvents sequentially from left to right, and one by one), suspension solution; with ultrasonication.

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 (Please use freshly prepared in vivo formulations for optimal results.)