Evofosfamide

Evofosfamide

Names
Preferred IUPAC name (1-Methyl-2-nitro-1H-imidazol-5-yl)methyl N,N′-bis(2-bromoethyl)phosphorodiamidate
Other names TH-302; HAP-302
Identifiers
CAS Number	918633-87-1^Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:231678
ChEMBL	ChEMBL260046
ChemSpider	10157061^Y
KEGG	D10704^Y
PubChem CID	11984561
UNII	8A9RZ3HN8W^Y
CompTox Dashboard (EPA)	DTXSID60238721
InChI InChI=1S/C9H16Br2N5O4P/c1-15-8(6-12-9(15)16(17)18)7-20-21(19,13-4-2-10)14-5-3-11/h6H,2-5,7H2,1H3,(H2,13,14,19)^Y Key: UGJWRPJDTDGERK-UHFFFAOYSA-N^Y
SMILES CN1C(=CN=C1[N+](=O)[O-])COP(=O)(NCCBr)NCCBr
Properties
Chemical formula	C9H16Br2N5O4P
Molar mass	449.040 g·mol^−1
Solubility in water	6 to 7 g/L
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Y verify (what is ^YN ?) Infobox references

Evofosfamide (INN,^[1] USAN;^[2] formerly known as TH-302) is a compound being evaluated in clinical trials for the treatment of multiple tumor types as a monotherapy and in combination with chemotherapeutic agents and other targeted cancer drugs.

This compound has been evaluated in the treatment of solid tumors, as a hypoxia-activated prodrug (HAPs), such chemical agents in low oxygen conditions undergo bio-reduction to yield cancer fighting cytotoxic breakdown products.

Many such agents have been developed, though this compound has been extensively studied, in preclinical and clinical studies.^{[3] [4]}

Collaboration

Evofosfamide was developed by Threshold Pharmaceuticals Inc. In 2012, Threshold signed a global license and co-development agreement for evofosfamide with Merck KGaA, Darmstadt, Germany (EMD Serono Inc. in the US and Canada), which includes an option for Threshold to co-commercialize evofosfamide in the United States. Threshold is responsible for the development of evofosfamide in the soft tissue sarcoma indication in the United States. In all other cancer indications, Threshold and Merck KGaA are developing evofosfamide together.^[5] From 2012 to 2013, Merck KGaA paid 110 million US$ for upfront payment and milestone payments to Threshold. Additionally, Merck KGaA covers 70% of all evofosfamide development expenses.^[6]

Mechanism of prodrug activation and Mechanism of action (MOA) of the released drug

Evofosfamide is a 2-nitroimidazole prodrug of the cytotoxin bromo-isophosphoramide mustard (Br-IPM). Evofosfamide is activated by a process that involves a 1-electron (1 e⁻) reduction mediated by ubiquitous cellular reductases, such as the NADPH cytochrome P450, to generate a radical anion prodrug:

• A) In the presence of oxygen (normoxia) the radical anion prodrug reacts rapidly with oxygen to generate the original prodrug and superoxide. Therefore, evofosfamide is relatively inert under normal oxygen conditions, remaining intact as a prodrug.
• B) When exposed to severe hypoxic conditions (< 0.5% O₂; hypoxic zones in many tumors), however, the radical anion undergoes irreversible fragmentation, releasing the active drug Br-IPM and an azole derivative. The released cytotoxin Br-IPM alkylates DNA, inducing intrastrand and interstrand crosslinks.^[7]

Evofosfamide is essentially inactive under normal oxygen levels. In areas of hypoxia, evofosfamide becomes activated and converts to an alkylating cytotoxic agent resulting in DNA cross-linking. This renders cells unable to replicable their DNA and divide, leading to apoptosis. This investigational therapeutic approach of targeting the cytotoxin to hypoxic zones in tumors may cause less broad systemic toxicity that is seen with untargeted cytotoxic chemotherapies.^[8]

The activation of evofosfamide to the active drug Br-IPM and the mechanism of action (MOA) via cross-linking of DNA is shown schematically below:

Drug development history

Phosphorodiamidate-based, DNA-crosslinking, bis-alkylator mustards have long been used successfully in cancer chemotherapy and include e.g. the prodrugs ifosfamide and cyclophosphamide. To demonstrate that known drugs of proven efficacy could serve as the basis of efficacious hypoxia-activated prodrugs, the 2-nitroimidizole HAP of the active phosphoramidate bis-alkylator derived from ifosfamide was synthesized. The resulting compound, TH-281, had a high HCR (hypoxia cytotoxicity ratio), a quantitative assessment of its hypoxia selectivity. Subsequent structure-activity relationship (SAR) studies showed that replacement of the chlorines in the alkylator portion of the prodrug with bromines improved potency about 10-fold. The resulting, final compound is evofosfamide (TH-302).^[9]

Synthesis

Evofosfamide's synthesis involves several steps, starting with the preparation of 2-nitroimidazole derivatives. Here’s a simplified overview of the process:

1. Preparation of 2-nitroimidazole: This is the key bioreductive group used in the synthesis.
2. Formation of the prodrug: The 2-nitroimidazole is linked to a brominated derivative of isophosphoramide mustard.
3. Activation under hypoxic conditions: In low oxygen environments, typical of solid tumors, the prodrug is activated to release the cytotoxic agent.

This synthesis method allows Evofosfamide to target hypoxic tumor cells selectively, making it a promising candidate in cancer therapy.^{[10][11][12][13]}

Formulation

The evofosfamide drug product formulation used until 2011 was a lyophilized powder. The current drug product formulation is a sterile liquid containing ethanol, dimethylacetamide and polysorbate 80. For intravenous infusion, the evofosfamide drug product is diluted in 5% dextrose in WFI.^[14]

Diluted evofosfamide formulation (100 mg/mL evofosfamide, 70% ethanol, 25% dimethylacetamide and 5% polysorbate 80; diluted to 4% v/v in 5% dextrose or 0.9% NaCl) can cause leaching of DEHP from infusion bags containing PVC plastic.^[15]

Clinical trials

Overview and results

Evofosfamide (TH-302) is currently being evaluated in clinical studies as a monotherapy and in combination with chemotherapy agents and other targeted cancer drugs. The indications are a broad spectrum of solid tumor types and blood cancers.

Evofosfamide clinical trials (as of 21 November 2014)^[16] sorted by (Estimated) Primary Completion Date:^[17]

Evofosfamide (TH-302) clinical trials in following indications: Solid Tumors, Soft Tissue Sarcoma, Pancreatic Cancer/Pancreatic Adenocarcinoma/Pancreatic Neuroendocrine Tumors, Non-Small Cell Lung Cancer, Melanoma, Prostate Cancer, Kidney Cancer/Renal Cell Carcinoma, Liver Cancer/Hepatocellular Carcinoma, Myelogenous Leukemia/Lymphocytic Leukemia, Myelodysplastic Syndrome, Myelofibrosis, Multiple Myeloma, Glioma/Glioblastoma, Gastrointestinal Stromal Tumors
NCT Number / Title	Other IDs	Start Date	(Estimated) Primary Completion Date	Recruitment	Conditions	Interventions	Phases	Enrollment (Patients)	Sponsor / Collaborators
NCT00495144 A Phase I Study of the Safety, Pharmacokinetics, and Anti-Tumor Activity of TH-302 in Patients With Advanced Solid Tumors	TH-CR-401	June 2007	December 2011	Completed	Tumors, Hypoxia	Drug: TH-302	Phase 1	129	Threshold Pharmaceuticals
NCT01149915 Study of Hypoxia-Activated Prodrug TH-302 to Treat Advanced Leukemias	TH-CR-407	June 2010	August 2013	Completed	Acute Myelogenous Leukemia, Acute Lymphoblastic Leukemia, Chronic Myelogenous Leukemia, High-risk Myelodysplastic Syndrome, Chronic Lymphocytic Leukemia, Advanced Myelofibrosis	Drug: TH-302	Phase 1	40	Threshold Pharmaceuticals
NCT01144455 Study of the Safety and Efficacy of TH-302 in Combination With Gemcitabine Compared With Gemcitabine Alone in Previously Untreated Patients With Pancreatic Adenocarcinoma	TH-CR-404	June 2010	August 2013	Completed	Pancreatic Adenocarcinoma	Drug: Gemzar (Gemcitabine), Drug: TH-302, Drug: TH-302	Phase 2	165	Threshold Pharmaceuticals, PRA Health Sciences
	Results: 30 March 2012[18][19] The study met its primary efficacy endpoint with a median increase in progression-free survival (PFS) from 3.6 months to 5.6 months in the pooled patients treated with TH-302 (at 240 mg/m2 or 340 mg/m2) in combination with gemcitabine compared to gemcitabine alone. In addition, a dose response was identified with the greatest efficacy in the higher 340 mg/m2 group with a median PFS of 6.0 months. 18 November 2014[20] gemcitabine alone (N=69): Median PFS of 3.6 months, median OS of 6.9 months. gemcitabine + TH-302 240 mg/m2 (N=71): Median PFS of 5.6 months, median OS of 8.7 months. gemcitabine + TH-302 340 mg/m2 (N=74): Median PFS of 6.0 months, median OS of 9.2 months.
NCT00742963 Dose-Escalation Study of TH-302 in Combination With Doxorubicin to Treat Patients With Advanced Soft Tissue Sarcoma	TH-CR-403	August 2008	September 2013	Completed	Soft Tissue Sarcoma	Drug: TH-302	Phase 1, Phase 2	102	Threshold Pharmaceuticals
	Results: 15 November 2012, Results for overall study population (N=91)[21][22] Median progression free survival of 6.7 months. Median overall survival of 21.5 months. 10 October 2014, Results for overall study population (N=91)[23] Median progression free survival of 6.5 months. Median overall survival of 21.5 months.
NCT00743379 Dose-Escalation Study of TH-302 in Combination With A) Gemcitabine or B) Docetaxel or C) Pemetrexed to Treat Advanced Solid Tumors	TH-CR-402	August 2008	September 2013	Completed	Non-Small Cell Lung Cancer, Prostate Cancer, Pancreatic Cancer	Drug: TH-302	Phase 1, Phase 2	71	Threshold Pharmaceuticals
	Results: 12 October 2010[24] In the gemcitabine treatment arm, 43 patients with advanced or metastatic pancreatic cancer were treated: Median progression-free survival (PFS) was 6.4 months and median overall survival (OS) was 11.4 months. In the TH-302 plus docetaxel or pemetrexed treatment arms of the trial, 32 patients with non-small cell lung cancer were treated: Median PFS was 4.2 months. 24 January 2011[25][26] In the gemcitabine plus TH-302 treatment arms, 47 patients with advanced or metastatic pancreatic cancer were treated: Median progression free survival was 5.9 months and median overall survival was 8.5 months. 18 November 2014[27][28] In the TH-302 plus pemetrexed treatment arm of the trial, 18 patients with non-small cell lung cancer were treated: Median PFS was 7.0 months. Median overall survival was 14.9 months.
NCT01497444 Sorafenib Tosylate and Hypoxia-Activated Prodrug TH-302 in Treating Patients With Advanced Kidney Cancer or Liver Cancer That Cannot Be Removed By Surgery	TH-IST-4004, N1153, NCCTG-N1153, CDR0000720022, NCI-2012-00095, U10CA031946	May 2012	January 2014	Recruiting	Kidney Cancer, Liver Cancer	Drug: hypoxia-activated prodrug TH-302, Drug: sorafenib tosylate, Genetic: protein analysis, Other: laboratory biomarker analysis	Phase 1, Phase 2	48	North Central Cancer Treatment Group, National Cancer Institute (NCI), Alliance for Clinical Trials in Oncology, Cancer and Leukemia Group B, American College of Surgeons, Threshold Pharmaceuticals
NCT01440088 A Trial of TH-302 in Combination With Doxorubicin Versus Doxorubicin Alone to Treat Patients With Locally Advanced Unresectable or Metastatic Soft Tissue Sarcoma	TH-CR-406 / SARC021	September 2011	June 2014	Active, not recruiting	Soft Tissue Sarcoma	Drug: TH-302 in Combination with Doxorubicin, Drug: Doxorubicin	Phase 3	620	Threshold Pharmaceuticals, Sarcoma Alliance for Research through Collaboration (SARC)
	Results: 18 September 2014[29] Final phase 3 results available in 2015. 22 September 2014[30] The planned interim efficacy and safety analyses has been completed: The trial will continue as planned to its natural conclusion. The estimated primary completion date has been revised to the latter half of 2015. 3 November 2014[31] Primary analysis of overall survival expected to be conducted in the first quarter of 2016.
NCT01381822 Dose-Escalation Study of TH-302 in Combination With Sunitinib to Treat Patients With Advanced Renal Cell Carcinoma, Gastrointestinal Stromal Tumors and Pancreatic Neuroendocrine Tumors	TH-CR-410	June 2011	June 2014	Active, not recruiting	Advanced Renal Cell Carcinoma, Gastrointestinal Stromal Tumors, Pancreatic Neuroendocrine Tumors	Drug: TH-302	Phase 1	58	Threshold Pharmaceuticals
NCT01833546 A Japanese Phase 1 Trial of TH-302 in Subjects With Solid Tumors and Pancreatic Cancer	EMR200592-002	April 2013	January 2015	Active, not recruiting	Solid Tumor, Pancreatic Cancer	Drug: TH-302 monotherapy, Drug: TH-302, Drug: Gemcitabine	Phase 1	20	Merck KGaA, Threshold Pharmaceuticals
NCT02020226 A Cardiac Safety Study of TH-302 in Patients With Advanced Solid Tumors	TH-CR-414	November 2013	January 2015	Recruiting	Solid Tumors	Drug: TH-302	Phase 1	40	Threshold Pharmaceuticals
NCT02076230 A Phase 1 TH-302 Mass Balance Trial	EMR200592-007, 2013-003950-25	February 2014	March 2015	Active, not recruiting	Solid Tumors	Drug: [14C] TH-302 (Label 1), Drug: [14C] TH-302 (Label 2), Drug: Unlabeled TH-302	Phase 1	10	Merck KGaA, Threshold Pharmaceuticals
NCT01522872 Open-label Study of TH-302 and Dexamethasone With or Without Bortezomib in Subjects With Relapsed/Refractory Multiple Myeloma	TH-CR-408	February 2012	June 2015	Recruiting	Multiple Myeloma	Drug: TH-302, Drug: TH-302, Drug: TH-302 and bortezomib	Phase 1, Phase 2	60	Threshold Pharmaceuticals
NCT01864538 A Phase 2 Biomarker - Enriched Study of TH-302 in Subjects With Advanced Melanoma	TH-CR-413	May 2013	June 2015	Recruiting	Metastatic Melanoma	Drug: TH-302	Phase 2	40	Threshold Pharmaceuticals
NCT01403610 Safety and Efficacy Study of TH-302 CNS Penetration in Recurrent High Grade Astrocytoma Following Bevacizumab	TH-IST-4003, CTRC 11-24	June 2011	July 2015	Recruiting	High Grade Glioma	Drug: TH-302, Drug: Placebo	Phase 2	34	The University of Texas Health Science Center at San Antonio
	Results: 30 May 2014[32][33] Median progression-free survival (PFS) of 3.1 months on combination therapy vs. 2.4 months on prior single-agent bevacizumab. 17 November 2014[34] Median progression-free survival (PFS) of 2.8 months on bevacizumab/TH-302 combination therapy (N=22). Median overall survival of 4.6 months on bevacizumab/TH-302 combination therapy (N=22).
NCT01721941 TH-302 Plus Doxorubicin Delivered by Trans-Arterial Chemoembolization (TACE) in Patients With Hepatocellular Carcinoma	TH302 TACE	December 2014	December 2015	Not yet recruiting	Hepatocellular Carcinoma	Drug: Phase I Dose level -1, Drug: Phase I dose level 1, Drug: Phase I Dose level 2, Drug: Phase I Dose level 3	Phase 1	20	Scripps Clinic Cancer Center, Threshold Pharmaceuticals
NCT01746979 Clinical Trial Testing TH-302 in Combination With Gemcitabine in Previously Untreated Subjects With Metastatic or Locally Advanced Unresectable Pancreatic Adenocarcinoma	MAESTRO, EMR 200592-001, 2012-002957-42	December 2012	February 2016	Active, not recruiting	Metastatic or Locally Advanced Unresectable Pancreatic Adenocarcinoma	Drug: TH-302, Drug: Gemcitabine, Drug: Placebo (5 percent dextrose - D5W)	Phase 3	660	EMD Serono, Threshold Pharmaceuticals
	Results: 3 November 2014[35] Target enrollment of 660 patients completed. Top-line data anticipated in 2016. 18 November 2014[36] Top-line data anticipated in Q1/2016.
NCT02047500 Phase I TH-302 Plus Gemcitabine Plus Nab-Paclitaxel in Pancreatic Cancer	EMR200592-006	January 2014	June 2016	Recruiting	Pancreatic Cancer	Drug: TH-302, Drug: Nab-paclitaxel, Drug: Gemcitabine	Phase 1	48	EMD Serono, Threshold Pharmaceuticals
NCT02093962 Study of TH-302 or Placebo in Combination With Pemetrexed in Patients With Non-squamous Non-small Cell Lung Cancer	TH-CR-415	March 2014	July 2016	Recruiting	Non-small Cell Lung Cancer	Drug: TH-302 combination with pemetrexed, Drug: Matched placebo in combination with pemetrexed	Phase 2	440	Threshold Pharmaceuticals, EMD Serono
	Results: 18 November 2014[37] Expect enrollment to be completed end of 2015.
NCT02255110 A Japanese Trial of TH-302 in Subjects With Locally Advanced Unresectable or Metastatic Soft Tissue Sarcoma	EMR200592-008	October 2014	October 2016	Recruiting	Soft Tissue Sarcoma	Drug: TH-302, Drug: Doxorubicin	Phase 2	46	Merck KGaA, Threshold Pharmaceuticals
NCT01485042 Dose Escalation Study of Pazopanib Plus TH-302	PATH, TH-IST-4001, Pro00031123	December 2011	December 2016	Active, not recruiting	Solid Tumors	Drug: Pazopanib and TH-302	Phase 1	50	Herbert Hurwitz, MD, National Comprehensive Cancer Network, GlaxoSmithKline, Threshold Pharmaceuticals, Duke University
EudraCT: 2014-004072-30 A phase II trial to assess the activity and safety of TH-302 in combination with sunitinib in patients with well- and moderately-differentiated metastatic pancreatic neuroendocrine tumors (pNET) previously untreated	GETNE-1408, EMR 200592-012	January 2015		Ongoing	Metastatic pancreatic neuroendocrine tumors (pNET)	Drug: TH-302 in combination with sunitinib	Phase 2	43	Grupo Español de Tumores Neuroendocrinos, MFAR, S.L., Spain
NCT02342379 TH-302 in Combination With Bevacizumab for Glioblastoma	TH-IST-4008, CTRC 12-0105	February 2015	February 2017	Not yet recruiting	Glioblastoma	Drug: Bevacizumab and TH-302	Phase 2	33	The University of Texas Health Science Center at San Antonio
Note: Results based on Response Evaluation Criteria in Solid Tumors (RECIST) assessments are not shown.

Soft tissue sarcoma

Both, evofosfamide and ifosfamide have been investigated in combination with doxorubicin in patients with advanced soft tissue sarcoma. The study TH-CR-403 is a single arm trial investigating evofosfamide in combination with doxorubicin.^[38] The study EORTC 62012 compares doxorubicin with doxorubicin plus ifosfamide.^[39] Doxorubicin and ifosfamide are generic products sold by many manufacturers.

The indirect comparison of both studies shows comparable hematologic toxicity and efficacy profiles of evofosfamide and ifosfamide in combination with doxorubicin. However, a longer overall survival of patients treated with evofosfamide/doxorubicin (TH-CR-403) trial was observed. The reason for this increase is probably the increased number of patients with certain sarcoma subtypes in the evofosfamide/doxorubicin TH-CR-403 trial, see table below.

However, in the Phase 3 TH-CR-406/SARC021 study (conducted in collaboration with the Sarcoma Alliance for Research through Collaboration (SARC)), patients with locally advanced unresectable or metastatic soft tissue sarcoma treated with evofosfamide in combination with doxorubicin did not demonstrate a statistically significant improvement in OS compared with doxorubicin alone (HR: 1.06; 95% CI: 0.88 - 1.29).^{[citation needed]}

Comparison of ifosfamide/doxorubicin with evofosfamide/doxorubicin in soft tissue sarcoma
Baseline Characteristics	Study ID	NCT00061984 Phase 3 trial EORTC 62012[40]		NCT01440088 Phase 2 trial TH-CR-403[41]
	Drug 1	Doxorubicin 75 mg/m^2 Day 1 or as a 72-hour continuous i.v. infusion	Doxorubicin 25 mg/m^2 Days 1-3	Doxorubicin 75 mg/m^2 Day 1
	Drug 2		Ifosfamide 2.5 g/m^2 Days 1-4	Evofosfamide 300 mg/m^2 Days 1, 8
	Drug 3		Pegfilgrastim 6 mg s.c. Day 5	Growth Factor Day 8 or Day 9
	Patients	N=228	N=227	N=91
	Median number of cycles	5 cycles	6 cycles	7 cycles (N = 91) + 10 maintenance cycles (n = 48)
	Number of patients with sarcoma subtype Leiomyosarcoma or Liposarcoma	35%	40%	52%
Efficacy	Median Progression-free survival	4.6 months	7.4 months	6.5 months
	Median Overall survival (OS)	12.8 months	14.3 months	21.5 months
	Median OS, Leiomyosarcoma patients			31.9 months
	Median OS, Liposarcoma patients			32.9 months
Hematologic Toxicity	Grade 3/4 Neutropenia	37%	42%	31%
	Grade 3/4 Febrile Neutropenia	13%	46%	8%
	Grade 3/4 Thrombocytopenia	< 1%	34%	32%
	Grade 3/4 Anemia	4%	35%	36%
	Grade 3/4 Leucopenia	18%	43%	N/A

Metastatic pancreatic cancer

Both, evofosfamide and protein-bound paclitaxel (nab-paclitaxel) have been investigated in combination with gemcitabine in patients with metastatic pancreatic cancer. The study TH-CR-404 compares gemcitabine with gemcitabine plus evofosfamide.^[42] The study CA046 compares gemcitabine with gemcitabine plus nab-paclitaxel.^[43] Gemcitabine is a generic product sold by many manufacturers.

The indirect comparison of both studies shows comparable efficacy profiles of evofosfamide and nab-paclitaxel in combination with gemcitabine. However, the hematologic toxicity is increased in patients treated with evofosfamide/gemcitabine (TH-CR-404 trial), see table below.

In the Phase 3 MAESTRO study, patients with previously untreated, locally advanced unresectable or metastatic pancreatic adenocarcinoma treated with evofosfamide in combination with gemcitabine did not demonstrate a statistically significant improvement in overall survival (OS) compared with gemcitabine plus placebo (hazard ratio [HR]: 0.84; 95% confidence interval [CI]: 0.71 - 1.01; p=0.0589).^{[citation needed]}

Comparison of gemcitabine/nab-paclitaxel with gemcitabine/evofosfamide in metastatic pancreatic adenocarcinoma
Baseline Characteristics	Study ID	NCT00844649 Phase 3 trial CA046[44]		NCT01144455 Phase 2 trial TH-CR-404[45]
	Drug 1	Gemcitabine 1 g/m^2 Schedule A	Gemcitabine 1 g/m^2 Schedule B	Gemcitabine 1 g/m^2 Schedule B	Gemcitabine 1 g/m^2 Schedule B	Gemcitabine 1 g/m^2 Schedule B
	Drug 2	---	nab-Paclitaxel 125 mg/m^2 Schedule B	---	Evofosfamide 240 mg/m^2 Schedule B	Evofosfamide 340 mg/m^2 Schedule B
	Drug 3	15% of patients received growth factors	26% of patients received growth factors	Optional: Growth factors	Optional: Growth factors	Optional: Growth factors
	Patients [N]	430	431	69	71	74
Efficacy	Median Progression-free survival [months]	3.7	5.5	3.6	5.6	6.0
	Median Overall survival [months]	6.7	8.5	6.9 (1)	8.7 (1)	9.2 (1)
Hematologic Toxicity	Grade 3/4 Neutropenia [%]	27	38	17	34	43
	Grade 3/4 Febrile Neutropenia [%]	1	3	N/A	N/A	N/A
	Grade 3/4 Thrombocytopenia [%]	9	13	12	30	55
	Grade 3/4 Anemia [%]	12	13	29	34	43
	Grade 3/4 Leucopenia [%]	16	31	N/A	N/A	N/A
Schedule A: Weekly for 7 of 8 weeks (cycle 1) and then on days 1, 8, and 15 every 4 weeks (cycle 2 and subsequent cycles) Schedule B: On days 1, 8 and 15 every 4 weeks (1) statistically not significant

Nasopharyngeal Carcinoma

Oxygen deficient conditions are linked to tumor progression throughout the body and poses an issue in cancer treatments such as chemotherapy and radiation.^[46] Hypoxia-activated prodrugs (HAPs) function in hypoxic conditions and inhibit the growth of tumor cells.^[47] Evofosfamide is a HAP that targets tumor progression in nasopharyngeal carcinoma (NPC) tissues by inhibitng the overexpression of hypoxia-inducible factor-1α (HIF-1α).^[48]

In this study , the efficacy of Evofosfamide along with cisplastin (DDP) in blocking cell progression was measured. "The combination of evofosfamide with DDP had a synergistic effect on cytotoxicity in the NPC cell lines by combination index values assessment. Cell cycle G2 phase was arrested after treated with 0.05 μmol/L evofosfamide under hypoxia. Histone H2AX phosphorylation (γH2AX) (a marker of DNA damage) expression increased while HIF-1α expression suppressed after evofosfamide treatment under hypoxic conditions".^[49] These findings allow for evidence for Evofosfamide to be pushed towards clinical trials to further investigate the potential to be developed as an FDA approved anticancer drug.

Drug development risks

Risks published in the quarterly/annual reports of Threshold and Merck KGaA that could affect the further development of evofosfamide (TH-302):

Risks related to the formulation

The evofosfamide formulation that Threshold and Merck KGaA are using in the clinical trials was changed in 2011^[50] to address issues with storage and handling requirements that were not suitable for a commercial product. Additional testing is ongoing to verify if the new formulation is suitable for a commercial product. If this new formulation is also not suitable for a commercial product another formulation has to be developed and some or all respective clinical phase 3 trials may be required to be repeated which could delay the regulatory approvals.^[51]

Risks related to reimbursement

Even if Threshold/Merck KGaA succeed in obtaining regulatory approvals and bringing evofosfamide to the market, the amount reimbursed for evofosfamide may be insufficient and could adversely affect the profitability of both companies. Obtaining reimbursement for evofosfamide from third-party and governmental payors depend upon a number of factors, e.g. effectiveness of the drug, suitable storage and handling requirements of the drug and advantages over alternative treatments.

There could be the case that the data generated in the clinical trials are sufficient to obtain regulatory approvals for evofosfamide but the use of evofosfamide has a limited benefit for the third-party and governmental payors. In this case Threshold/Merck KGaA could be forced to provide supporting scientific, clinical and cost effectiveness data for the use of evofosfamide to each payor. Threshold/Merck KGaA may not be able to provide data sufficient to obtain reimbursement.^[52]

Risks related to competition

Each cancer indication has a number of established medical therapies with which evofosfamide will compete, for example:

• If approved for commercial sale for pancreatic cancer, evofosfamide would compete with gemcitabine (Gemzar), marketed by Eli Lilly and Company; erlotinib (Tarceva), marketed by Genentech and Astellas Oncology; protein-bound paclitaxel (Abraxane), marketed by Celgene; and FOLFIRINOX, which is a combination of generic products that are sold individually by many manufacturers.
• If approved for commercial sale for soft tissue sarcoma, evofosfamide could potentially compete with doxorubicin or the combination of doxorubicin and ifosfamide, generic products sold by many manufacturers.^[53]

Risks related to manufacture and supply

Threshold relies on third-party contract manufacturers for the manufacture of evofosfamide to meet its and Merck KGaA's clinical supply needs. Any inability of the third-party contract manufacturers to produce adequate quantities could adversely affect the clinical development and commercialization of evofosfamide. Furthermore, Threshold has no long-term supply agreements with any of these contract manufacturers and additional agreements for more supplies of evofosfamide will be needed to complete the clinical development and/or commercialize it. In this regard, Merck KGaA has to enter into agreements for additional supplies or develop such capability itself. The clinical programs and the potential commercialization of evofosfamide could be delayed if Merck KGaA is unable to secure the supply.^[54]

History

Date	Event
Jun 2005	Threshold files evofosfamide (TH-302) patent applications in the U.S.[55]
Jun 2006	Threshold files an evofosfamide (TH-302) patent application in the EU and in Japan[56]
Sep 2011	Threshold starts a Phase 3 trial (TH-CR-406) of evofosfamide in combination with doxorubicin in patients with soft tissue sarcoma
Feb 2012	Threshold signs an agreement with Merck KGaA to co-develop evofosfamide
Apr 2012	A Phase 2b trial (TH-CR-404) of evofosfamide in combination with gemcitabine in patients with pancreatic cancer meets primary endpoint
Jan 2013	Merck KGaA starts a global Phase 3 trial (MAESTRO) of evofosfamide in combination with gemcitabine in patients with pancreatic cancer
Dec 2015	two Phase 3 trials fail, Merck will not apply for a license^[citation needed]

References

1. WHO Drug Information; Recommended INN: List 73
2. Adopted Names of the United States Adopted Names Council
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4. "Evofosfamide". go.drugbank.com. Retrieved 2023-11-03.
5. "Threshold Pharmaceuticals and Merck KGaA Announce Global Agreement to Co-Develop and Commercialize Phase 3 Hypoxia-Targeted Drug TH-302 - Press release from 3 February 2012". Archived from the original on 25 October 2014. Retrieved 25 October 2014.
6. "Threshold Pharmaceuticals Form 8-K from 3 Nov 2014". Archived from the original on 6 November 2014. Retrieved 5 November 2014.
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