JONT Journal

The synthetic retinoid fenretinide (4-HPR) has been employed in numerous cancer clinical trials in recent decades. In these trials, administration of fenretinide alone demonstrated low bioavailability [38]. Recent developments have incorporated fenretinide with other agents to stimulate a synergistic increase in efficacy against malignancies. One clinical trial combined fenretinide with ketoconazole to interfere with the breakdown of fenretinide by the body before it reached the tumor microenvironment [ClinicalTrials.gov Identifier: NCT01535157]. According to the Clinical Trials Registry this trial was terminated due to the lack of efficacy using the combination of fenretinide with ketoconazole. However, it did note that the data gained from that trial may be used for a subsequent trial. Interestingly, fenretinide has also been investigated in combination with the acid CDase (A-CDase) inhibitor DM102 [26]. A-CDase breaks down ceramide to sphingosine and is a rate-limiting step in the biosynthesis of pro- survival and pro-mitogenic S1P. In this study, the combination of DM102 and fenretinide enhanced ceramide generation, produced ROS, blocked metastasis, and induced apoptosis in prostate cancer [26]. In contrast, either compound alone was not able to achieve the same outcomes. Additionally, there has been a phase I trial of fenretinide in combination with intravenous administration of the SPHK1 inhibitor safingol [ClinicalTrials.gov Identifier: NCT01553071] [39]. This study ended earlier than originally planned due to drug supply issues related to the COVID-19 pandemic. However, enough data was generated for some meaningful results. Nearly 90% of the enrolled patients experienced hypertriglyceridemia as an adverse event with over two thirds of those experiencing it as grade 3 or greater. Notably, hypertriglyceridemia as an adverse event in this trial was attributed to the intralipid infusion vehicle for the fenretinide. Unfortunately, one patient experienced dose-limiting toxicities at higher safingol dosage including grade 3 troponinemia and grade 4 myocarditis. Stable disease in two patients (~18%) was the only evidence of minimal activity for this combinatorial therapy although this was a small phase I trial. It should be noted that while ceramide generation has been attributed to fenretinide, it actually stimulates increases in dihydroceramide and other dihydro-sphingolipid species due to blockade of dihydroceramide desaturase. In the context of this clinical trial with safingol, a SPHK1 inhibitor, this may be particularly important as this inhibitory effect would mostly limit the generation of dhS1P than S1P given the fenrettide-induced increase in dihydro-sphingolipid species including dihydrosphingosine. While S1P is a pro-survival and pro-oncogenic sphingolipid, the same may not be the case for dhS1P. In preclinical in vivo studies, dhS1P and a nanotherapeutic approach that stimulates dhS1P were shown to exert antitumor efficacy in part by promoting an antitumor immune response [40]. Therefore, it would be interesting to see safingol be evaluated in a clinical trial in combination with a therapeutic that delivers ceramide so that the safingol effect would be directed more appropriately towards S1P generation.

Flavonoids such as hesperidin and naringenin, are found prominently in citrus fruits. Hesperidin has been shown to elevate intracellular ceramide levels by decreasing A-CDase enzymatic activity in melanoma and renal cell carcinoma cells [31]. Interestingly, hesperidin has also been identified as a HER2 tyrosine kinase inhibitor in breast cancer [32]. The compound called ceranib-2 is another A-CDase inhibitor which has demonstrated efficacy in inducing both early and late apoptosis in prostate, breast, and non-small-cell lung cancers [26-29]. This compound was found to be more effective than two older A-CDase inhibitors, D-MAPP and NOE (N-oleoylethanolamine) [28]. Like other A-CDase inhibitors, this compound is being examined for synergistic enhancing qualities with other chemotherapeutics such as paclitaxel and carboplatin [28].

Suramin is an older medication that is used in treating sleeping sickness due to trypanosome infection. Interestingly, it also is an inhibitor of S1PR3 and S1PR5 [14, 30]. Therefore, the sphingolipid-directed aspect of this compound mainly reduces pro- survival signaling associated with S1P, although it has also been shown to induce ceramide generation. Suramin has completed several clinical trials for the treatment of different cancers, including a phase I trial for the treatment of superficial transitional cell carcinoma of the bladder [ClinicalTrials.gov Identifier: NCT00001381], phase I/II trials of combinatorial treatment with paclitaxel for breast cancer [ClinicalTrials.gov Identifier: NCT00054028] and suramin with carboplatin and paclitaxel for treating non-small cell lung cancer [ClinicalTrials. gov Identifier: NCT00006929], and a phase III trial determining the effects of three different doses of suramin for the treatment of prostate cancer [ClinicalTrials.gov Identifier: NCT00002723] [41-44]. Clinical trials using suramin for cancer have generally found it to be well tolerated as a standalone agent as evidenced by rare and low-grade adverse events. Antitumor efficacy for suramin alone may be minimal. However, it may have palliative efficacy at low dose as it decreased depression and improved the quality of life in patients with metastatic prostate cancer [44]. This effect of decreasing depression is of note given the presence and roles of S1PRs in the brain. In contrast, trials evaluating suramin in combination with other therapeutics have had mixed results. Rates of adverse events are generally higher with some studies reporting somewhat frequent grade 3 and 4 events including anemia and neutropenia, as well as some patients discontinuing treatment due to these toxicities [42, 43]. Generally, combination therapy did not yield efficacy in these trials with patients had already developed chemoresistance. However, combinatorial therapy with suramin seems to have some efficacy in chemotherapy-naive patients [43]. Therefore, suramin appears to have some promise as an anticancer agent if in the right therapeutic combination. Additional studies continue to evaluate suramin, but the intent continues to be of an old drug repurposing nature and not because of suramin’s ability to inhibit S1PR3 and S1PR5 signaling. However, there are yet to be any studies specifically uniting suramin with ceramide-based therapeutics. Perhaps better responses to S1PR modulation would be seen in the context of other ceramide/sphingolipid-directed therapies.

The world of natural products-based drug discovery has also leveraged ceramide metabolism for the identification of therapeutics. Natural products are often sourced from plants or fungi for investigation into their intrinsic anticancer properties. The antioxidant resveratrol is considered a chemo preventative natural product which can increase ceramide generation in cancer cells [45, 46]. Our lab has explored the ability of multiple Alaskan ethnobotanicals such as Devil’s Club to decrease the viability of many cancers including acute myeloid leukemia (AML), pancreatic, and colorectal carcinoma. The Alaskan Bog Blueberry (Vaccinium uliginosum) is famous in the world of natural products-based drug discovery for its history of medicinal uses and applications. Bioactive compounds such as the pentacyclic triterpene ursolic acid are found in Alaskan Bog Blueberries and other medicinal plants such as Northern Labrador Tea (also known as Tundra Tea), Devil’s Club, plantain leaves, thyme, and coffee [47-49]. The mechanism of action of ursolic acid in cancer cells is still under investigation, but it is generally known for its pro-apoptotic and protective effects. It is hypothesized that the bioactive compounds in these plants may act through various mechanisms which alter sphingolipid metabolism to maintain heightened ceramide levels in cancer cells. Such mechanisms include increasing the activity of enzymes involved in ceramide generation while decreasing the activity of those involved in its elimination or neutralization.

Sphingolipid Metabolism and Regulating Anticancer Theraputics

An established target for the regulation of sphingolipid metabolism in cancer are the SPHKs, which generate S1P. As previously noted, S1P is involved in the survival pathways that are commonly manipulated by cancers, thus deeming SPHKs as targets for the development of therapeutics. For instance, as S1P is a regulator of tumor angiogenesis, SPHK and S1PR inhibitors are being used to enhance the efficacy of anti-angiogenic therapies [13, 15, 50]. These SPHK and S1PR inhibitors include small molecules, lipid mimetics, and immunomodulators. Initial SPHK inhibitors included sphingosine analogs such as dimethylsphingosine (DMS), coumarin-linked DMS, safingol as mentioned above, and sphingosine-based SK1-I [51-54] (Table 2) (Figure 1). The immunomodulator FTY720 (Gilenya, fingolimod) has been approved by the Federal Drug Administration (FDA) for the treatment of multiple sclerosis. It has been additionally investigated for its ability to act as a SPHK1 antagonist. This compound is a structural analog of sphingosine, which has been shown to bind SPHK1 competitively. Other targets of this drug include protein phosphatase 2A (PP2A), the PI3K/AKT pathway, and inhibition of mitochondrial permeability transition pore (MPTP) formation [33]. This drug has also been found to sensitize cancer cells to other chemotherapies including 5-fluorouracil, oxaliplatin, cetuximab, and sunitinib (Sutent) [55, 56]. Despite these findings, hope for FTY720 as a standalone chemotherapeutic is low, as this compound has exhibited high levels of toxicity and immunosuppressive effects on regulatory T cells [33]. Although, a new clinical trial evaluating FTY720 (Gilenya, fingolimod) is planned for non-small cell lung cancer and small cell lung cancer patients whose disease has progressed during chemo-immunotherapy [ClinicalTrials. gov Identifier: NCT06424067]. There have recently been several new drug approvals for compounds that selectively target S1PRs for the treatment rheumatoid conditions such as ulcerative colitis, including ozanimod (Zeposia) [57, 58] (Figure 1). Given links between chronic inflammation and the development and progression of cancer, it may not be surprising if these compounds are further investigated for anticancer efficacy.

Table 2: Specific Sphingolipid-Regulating Therapeutics.

The humanized S1P monoclonal antibody sonepcizumab (ASONEP) began phase II clinical trials for the treatment of renal cell carcinoma (ClinicalTrials.gov Identifier: NCT01762033). The trial was terminated due to the drug’s failure to meet the primary progression-free survival endpoint, although notable overall survival results (21.7 months) in patients with metastatic renal cell carcinoma may retain hope for this compound as a cancer therapeutic with continued research [59].

The SPHK inhibitor ABC294640 (Yeliva, opaganib) has demonstrated efficacy in multiple clinical trials. This compound is believed to possess notable efficacy due to its specificity for inhibiting SPHK2 [60, 61]. Completion of phase I trials in patients with advanced solid tumors saw ABC294640 meet primary and secondary endpoints. This trial demonstrated that it was well tolerated, with a notable decrease in S1P levels as well as disease stabilization in many cases [ClinicalTrials.gov Identifier: NCT01488513] [60]. There was a single patient in the lowest dosage (250 mg qd) cohort that experienced a doselimiting grade 4 instance of hyperglycemia but that was attributed to pancreatic failure due to their rapidly progressing pancreatic cancer. Otherwise, only low-grade adverse events were observed for patients during low and mid dosages (250 mg qd, 250 mg bid, and 500 mg bid), mostly including nausea, vomiting, and fatigue, alongside rare low-grade nervous system and neuropsychiatric adverse events. This contrasted with the highest dosage (750 mg bid) evaluated where there was an instance of dose-limiting grade 3 nausea and vomiting as well as two other instances of patients unable to complete treatment due to multiple grade 2 and 3 adverse events to include chest discomfort, choking sensation, dysarthria, acute kidney injury, nausea, and agitation. Ultimately, the highest dosage of ABC294640 evaluated was determined to not be tolerable. However, at tolerable lower dosage there were some indicators of efficacy with 40% patients having stable disease and one heavily pretreated cholangiocarcinoma patient experiencing an initial partial response. Unsurprisingly, there are multiple follow-on clinical trials evaluating ABC294640 including for cholangiocarcinoma [ClinicalTrials.gov Identifiers: NCT03377179 and NCT03414489], as well as metastatic castration-resistant prostate cancer [ClinicalTrials.gov Identifier: NCT04207255], and relapsed/refractory multiple myeloma [ClinicalTrials.gov Identifier: NCT02757326]. In the later study, performed with patients that had previously been exposed to proteasome inhibition and immunomodulatory therapies, ABC294640 was well-tolerated even at the higher dosage (750 mg bid) that was limiting in the earlier solid tumor trial. The most common adverse event was lowgrade neutropenia. Notably, as a phase I study, one patient had a partial response and another stable disease indicative of minimal efficacy in this difficult to treat relapsed/refractory multiple myeloma patient population [62]. Altogether, it is not surprising that the FDA has given Yeliva (ABC294640, opaganib) orphan drug designation for the treatment of cholangiocarcinoma as well as recently for neuroblastoma.

Ceramide Analogs for Cancer Therapy

The delivery of exogenous ceramide has existed as a cancer therapeutic strategy for many years now (Figure 1). This strategy is hindered by the intrinsic insolubility of ceramide. To overcome this hurdle, ceramide analogs have been developed which offer greatly increased solubility levels in the human body (Table 3). Short chain ceramides were created for this purpose. Shortening the length of the ceramide molecule modestly increases its solubility, while maintaining relatively similar interactions inside cells [50, 63-66]. Despite the improvement, these ceramide analogs simply are not soluble enough to enable proper efficacy alone. However, with the help of novel delivery systems, including various nanotechnologies, these short chain ceramides can be utilized. Other ceramide analogues include uracil-linked ceramides, ceramines, serinamides, serinols, N-substituted sphingosines, and 4,6-diene-ceramide [67-76]. These ceramide analogs often serve as inhibitors of ceramide neutralization (elimination) enzymes. CDases, which are inherently enzymes that can neutralize ceramide, are important lipid hydrolases that metabolize ceramide into sphingosine. CDases lower cellular ceramide levels while also catalyzing a rate-limiting step in the formation of pro-survival S1P. Multiple classes of CDases exist to function at varying pH optimums. A-CDase is highly upregulated in many cancers including in AML [77]. Neutral CDase and three different alkaline CDases also exist. The ability to break down ceramide into other lipids with varying cellular effects has flagged A-CDase as an important target for the development of many cancer therapeutics.

Table 3: Ceramide Analogs for Cancer Therapy.

A series of improved versions of the ceramide analog B-13 have been developed. These compounds, including LCL521, LCL204, and LCL385, boast improved structures based on B-13, with the enhanced ability of improved access to the lysosome where A-CDase is mainly located. LCL521 has demonstrated the ability to cause myeloid derived suppressor cell death by means of cathepsin B and D activated by lysosomes [78, 79]. Combinatorial applications of this compound with ionizing radiation or tamoxifen have shown enhanced efficacy versus either treatment independently [79]. The compound LCL204 has been shown to inhibit A-CDase activity and increase ceramide levels in AML. When murine AML cells and human AML patient samples were treated with LCL204, C16 and C24 ceramide levels were increased while the anti-apoptotic MCL-1 protein was decreased. Collectively, this led to a marked rise in apoptosis of the leukemia cells. Survival in a murine AML model treated with LCL204 also was significantly increased [77].

Novel Delivery Systems for Ceramide-Based Anticancer Theraputics

Sphingolipid-based therapeutics face the common obstacle of limited solubility. This hinders the efficacy of these commonly hydrophobic molecules, as they cannot diffuse into cells independently. Novel delivery systems have been developed to circumvent this challenge, and to provide increased selective delivery to tumor microenvironments. Nanoscale delivery systems include nanoliposomes, calcium phosphosilicate nanoparticles (CPSNPs), thermoresponsive and biodegradable linear dendritic nanoparticles, nanoemulsions, polyepsilon-caprolactone nanoparticles, C6 ceramides-oxidized graphene nanoribbons (O-GNRs), and C6 ceramide graphene nanoplatelets (GNPs) [8096] (Table 4) (Figure 1).

Table 4: Ceramide-Delivering Nanoscale Systems.

The CPSNP technology presents an effective drug delivery system by means of a stable, non-aggregating calcium phosphate particle loaded with ceramide. These particles are 20 nm in diameter, and they can function as methods for bioimaging or as nano delivery systems for ceramide and other insoluble chemotherapies. This resorbable system takes advantage of pH changes in the cellular endosomal-lysosomal pathway for the selective delivery and release of the particle’s contents. Lower intracellular pH levels promote dissolution of the CPSNP structure, resulting in controlled release of the contained payload [89].

Suhrland et al. created a method to load short chain C6 ceramides onto oxidized graphene nanoribbons (O-GNRs) and graphene nanoplatelets (GNPs) [96]. Oxidation of the graphene nanoribbons allows for increased solubility, while retaining hydrophobic regions for the binding of ceramides. They tested both C6 ceramideloaded graphene nanoparticles for the ability to decrease HeLa cell viability. It was found that 100 µg/mL of C6 ceramide-loaded O-GNRs reduced cell viability by approximately 93%, while C6 ceramide-loaded GNPs reduced cell viability by approximately 76% [96].

Most notably, advances in nanoliposomal formulations for the delivery of sphingolipid chemotherapeutics have been established in the last decade. Kester et. al began navigating the clinical development of the C6 ceramide nanoliposome (CNL) [81]. CNL is composed of various lipids, including a “drug-like” C6 ceramide analog along with other lipids including a polyethylene glycol (PEG) modified C8 ceramide analog. This CNL therapy is administered intravenously, and thereafter C6 ceramide is delivered to cancer cells through intrabilayer exchange. Selective delivery of the CNL to solid tumor microenvironments is due primarily to the enhanced permeation and retention effect caused by the characteristic ‘leakiness’ of tumor vasculature. Treatment of multiple cancer models demonstrated the ability of CNL treatment to induce apoptosis and limit vascularization by inhibiting VEGF production, ERK and AKT phosphorylation, as well as expression of CD31 and CD105 [86]. Interestingly, one mechanism of action by which CNL treatment induces apoptosis in cancer cells is by interfering with glycolysis. This results in cell death as cancer cells often rely heavily on glycolysis to allow for increased growth rates, a phenomenon known as the Warburg effect [87].

The CNL therapy has been extensively studied by Kester et al. to determine necessary characteristics of the therapy such as pharmacokinetics and pharmacodynamics for the translation of this drug from the bench to the clinic. In collaboration with the Nanotechnology Characterization Laboratory of National Cancer Institute, it was determined that the CNL therapy has a greatly improved half-life (11-15 hours) in comparison to non-liposomal C6 ceramide (<3 minutes). Non-liposomal delivery of ceramide in DMSO has an LD50 of 10 mg/kg, while the CNL demonstrated no lethality at doses up to 100 mg/kg [81]. The inclusion of PEGylated ceramide in the formulation allows for added stability and enables evasion from immune destruction. The CNL also demonstrated very limited toxicity. The minor toxicity which does present is associated with the overall lipid composition of the nanoliposome and can be prevented by pretreatment with antihistamines [81]. The demonstrated efficacy of this chemotherapeutic, paired with its minimal toxicity level, highlights CNL as a promising and exciting example of sphingolipid-based therapeutics.

Notably, CNL has recently completed a phase I clinical trial with patients impacted by various advanced-stage solid tumor malignancies [ClinicalTrials.gov Identifier: NCT02834611] [97]. The patients in this trial all had metastatic disease, had prior surgery, and had been heavily treated with chemotherapy and/or radiation therapy. For the trial, pre-medication was given prior to liposomal infusion to prevent hypersensitivity reactions typical with lipid formulations. The trial evaluated multiple dosages including 36 mg/m2, 54 mg/m2, 81 mg/m2, 122 mg/m2, 183 mg/ m2, 215 mg/m2, and 323 mg/m2, given twice per week with four weeks equating to one cycle of therapy. The only adverse events related to treatment were grade 1 or 2 and occurred in 53% of the patients. These adverse events mostly included headache, constipation, nausea, fatigue, and transaminitis. They were minor and manageable, and so there was no dosage reduction or discontinuation of the study. Importantly, there were no dose- limiting toxicities, and a maximum tolerated dose was not reached. Notably, the highest dosage evaluated represented the maximum allowable infusion volume. Most notably, 38% of patients had stable disease after 8 weeks of treatment and one patient with pancreatic cancer continued to have stable disease until tumor progression at 24 weeks. Overall, CNL is quite promising as a therapeutic given these indicators of efficacy alongside it being very well-tolerated with no reported dose-limiting toxicities [97]. Importantly, CNL therapy may be most promising in combination with other therapeutics as several preclinical studies indicated [81].

The success of the CNL modality has encouraged subsequent investigations with this therapy including synergistic experiments with other standard of care cancer drugs. The CNL treatment has shown synergy with chemotherapeutics such as sorafenib, PPMP, FTY720, gemcitabine, and tamoxifen [61]. Our lab recently published our findings employing combinatorial CNL with vinblastine to treat AML and AML with myelodysplastic syndrome-related changes (AML-MRC). Vinblastine is a microtubule destabilizing agent which interferes with transport of vesicles. This study demonstrated that AML-MRC possesses increased sensitivity to CNL versus De Novo AML, and that the combinatorial therapy of CNL and vinblastine allows for the treatment of both diseases with increased efficacy [82]. Additionally, CNL was recently shown to have combinatorial anti-AML efficacy in preclinical models alongside the standard care therapeutics venetoclax and cytarabine [98]. Importantly, another clinical trial with CNL is planned and this time for patients with relapsed/refractory AML [ClinicalTrials.gov Identifier:

NCT04716452]. This upcoming trial is well-positioned to advance the clinical knowledge of CNL, given the recent preclinical studies highlighting the efficacy of CNL alone or in combination with other chemotherapeutics for AML [82, 98].

Biomarkers and Sphingolipid-Based Therapy

In cancer, sphingolipid metabolism can be dysregulated but not because of mutations to the genes encoding sphingolipid metabolic enzymes or signaling proteins. Rather, the dysfunction that does occur is secondary to molecular alterations typically used to diagnose, risk stratify patients and guide them to therapy. Indeed, many of the sphingolipid-directed therapeutics discussed in this review would likely be more effective if patient populations were identified and targeted for therapy using specific sphingolipidsignatures. One could envision screening to assess the prevalence or upregulation of targets, such as SPHK2 or S1PR1 to guide therapies such as ABC294640 (Yeliva, opaganib) or FTY720 (fingolimod, Gilenya), respectively. Another approach would be to study the sphingolipid metabolic profile of tumors or plasma. This type of “sphingolipidomic” evaluation is commonly done in research laboratories and can be adapted to clinical settings. This was done for the initial clinical trial studying CNL to enable pharmacological studies [97]. Sphingolipidomic profiling could reveal a metabolic signature that can both help select an appropriate sphingolipid-targeted therapeutic as well as follow the treatment for indication of the development of resistance, such as the upregulation of alternative metabolic pathways. Notably, sphingolipidomic approaches have been used in risk prediction for atherosclerosis and cardiovascular disease [99]. More specifically, ratios of different acyl chain lengths and degrees of saturation for various species of ceramide has been leveraged as a ceramide score to evaluate atherosclerosis and cardiovascular disease risk. This demonstrates that this methodology is beginning to be clinically available and could similarly be adapted for cancer.

Finally, a recent study used sphingolipidomic and genomic (transcriptomic) approaches to stratify AML exclusively based on a sphingolipid profile [100]. The study defined two distinct subtypes based on the prevalence of sphingomyelins (SM) and hexosylceramides (Hex) (glucosylceramide and galactosylceramide). Moreover, a classifier was developed that could leverage genomic data alone and was used to validate the subtypes using both the TCGA-AML and BEAT AML datasets. The HexlowSMhigh subtype had a significantly worse clinical outlook also was associated with a stem cell-like profile. The HexhighSMlow subtype still had a dismal clinical outlook but was instead associated with an inflammatory profile. One could envision many roles for this AML sphingolipid classifier including patient risk stratification but also therapy guidance. For instance, AML patients in the HexlowSMhigh subtype could be directed to therapies that elevate or deliver ceramide in combination with inhibition of the pathways leading to sphingomyelin generation. It may be possible that the approach used to develop this AML sphingolipid classifier could be adapted for other cancers. Similarly, the sphingolipidomic and genomic (transcriptomic) approaches could be used to identify unique sphingolipid signatures that can guide sphingolipid-targeted treatment selection.

Conclusions

Summarizing the current repertoire of sphingolipid metabolismmodulating cancer therapeutics highlights the potential that lies in both established and new drugs. The goal of these therapeutics is commonly to shift the balance of the ceramide/S1P biostat such that higher ratios of the pro-apoptotic lipid ceramide will induce cell death. This goal can be reached in many ways, such as by impacting the enzymes which metabolize ceramide, blocking S1P production, or by administering ceramide or ceramide analogs via nanoliposomal or other delivery systems. The limits to how useful these therapies can be for fighting cancer is set by the limits of our current understanding of sphingolipid biology. As we uncover more about the actions of these lipids, we can review previously established drugs for their potential to modulate sphingolipid metabolism in a helpful way or investigate how sphingolipid metabolism may explain the resistance that develops to current therapies. Additionally, further research into how cancer cells modulate sphingolipid metabolism for their survival will allow us to better leverage such signatures for the development of more targeted cancer therapies.

Acknowledgements

This work was funded in part by grants from the National Cancer

Institute of the National Institutes of Health to BMB (K22CA190674, R03-CA252825, and P01-CA171983 via subaward from the University of Virginia), as well as from the National Institute of General Medical Sciences of the National Institutes of Health to BMB (University of New Hampshire COBRE award P20-GM113131, and Alaska INBRE award P20-GM103395). BMB is the owner and founder of Tahosa Bio, LLC (Rapid City, SD).

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