Irofulven (DB05786): A Comprehensive Monograph on a Resurrected Antineoplastic Agent

Executive Summary

Irofulven is a novel, first-in-class, semisynthetic antineoplastic agent belonging to the acylfulvene family of experimental cancer drugs. Its development represents a compelling narrative in modern oncology, tracing its origins from a highly toxic natural product to a potential precision therapeutic. The compound is a structural analog of illudin S, a sesquiterpene toxin isolated from the poisonous and bioluminescent fungus Omphalotus illudens, commonly known as the Jack O'Lantern mushroom.[1] The parent compound, illudin S, exhibited potent antitumor activity but was deemed too toxic for clinical use, prompting a successful medicinal chemistry campaign to synthesize derivatives with an improved therapeutic index, culminating in the creation of Irofulven.[4]

Functionally, Irofulven is a DNA alkylating agent that operates through a distinctive mechanism of action. It is a prodrug that requires intracellular bioactivation by the enzyme alkenal/one oxidoreductase (AOR), also known as Prostaglandin Reductase 1 (PTGR1).[1] Upon activation, it forms highly reactive electrophiles that create unique DNA adducts, leading to the inhibition of DNA replication, S-phase cell cycle arrest, and the induction of apoptosis.[1] A key feature that distinguishes Irofulven from conventional alkylating agents is its ability to circumvent common mechanisms of drug resistance, including those mediated by p53 mutations and the overexpression of the MDR1 efflux pump.[1]

The clinical journey of Irofulven has been marked by periods of both high expectation and significant setbacks. After demonstrating considerable promise in preclinical models, it was granted "fast track" status by the U.S. Food and Drug Administration (FDA) in 2001.[1] However, subsequent clinical trials in broad, unselected patient populations across various solid tumors yielded modest and often statistically insignificant efficacy, which, combined with a challenging toxicity profile, led to the discontinuation of many studies and its characterization as a "previously abandoned" anticancer drug.[11] The modern resurgence of interest in Irofulven is driven by a paradigm shift towards precision oncology. Seminal discoveries have identified critical predictive biomarkers that can identify patient subpopulations with a high likelihood of response. Specifically, the efficacy of Irofulven is mechanistically linked to deficiencies in the transcription-coupled Nucleotide Excision Repair (TC-NER) DNA damage response pathway.[11] This creates a synthetic lethal interaction, positioning Irofulven as a promising targeted agent for tumors harboring these specific molecular vulnerabilities. Its development trajectory serves as a powerful case study in how a deeper understanding of molecular oncology can resurrect and redefine the therapeutic potential of an investigational agent.

Section 1: Physicochemical Profile and Molecular Taxonomy

This section provides a definitive reference for the chemical identity, structural characteristics, and pharmacological classification of Irofulven, establishing the fundamental properties of the molecule.

1.1 Nomenclature and Identifiers

To ensure clarity and facilitate cross-referencing across scientific literature and regulatory databases, the compound is identified by a range of names and registry numbers.

• Generic Name: Irofulven [10]
• Systematic (IUPAC) Names: Due to the molecule's complex spirocyclic structure, multiple systematic names appear in chemical databases. The most commonly cited include:
• (5'R)-5'-hydroxy-1'-(hydroxymethyl)-2',5',7'-trimethylspiro[cyclopropane-1,6'-indene]-4'-one [1]
• (6′R)-6′-Hydroxy-3′-(hydroxymethyl)-2′,4′,6′-trimethylspiro[cyclopropane-1,5′-inden]-7′(6′H)-one [11]
• Synonyms and Code Names: Throughout its development, Irofulven has been referred to by several alternative names and alphanumeric codes. These include 6-hydroxymethylacylfulvene, hydroxymethylacylfulvene, HMAF, MGI-114, MGI 114, and NSC 683863.[6]
• Registry and Database Identifiers:
• CAS Number: 158440-71-2 [1]
• DrugBank ID: DB05786 [1]
• UNII (Unique Ingredient Identifier): 6B799IH05A [1]
• ChEMBL ID: CHEMBL118218 [1]
• PubChem CID: 148189 [11]
• NCI Thesaurus Code: C1717 [1]

1.2 Chemical Structure and Properties

The molecular structure of Irofulven is the basis for its unique biological activity. Its key properties are summarized below.

• Molecular Formula: C15​H18​O3​ [1]
• Molecular Weight: 246.31 g/mol (Average); 246.1256 g/mol (Monoisotopic) [11]
• Structural Descriptors:
• SMILES: CC1=C(C2=C(C3(CC3)[C@@](C(=O)C2=C1)(C)O)C)CO [1]
• InChI: InChI=1S/C15H18O3/c1-8-6-10-12(11(8)7-16)9(2)15(4-5-15)14(3,18)13(10)17/h6,16,18H,4-5,7H2,1-3H3/t14-/m0/s1 [1]
• InChIKey: NICJCIQSJJKZAH-AWEZNQCLSA-N [1]
• Physical Properties:
• Appearance: Orange Solid [15]
• Melting Point: 127-129 °C [15]
• Density: 1.3±0.1 g/cm³ [15]
• Boiling Point (Predicted): 501.0±45.0 °C at 760 mmHg [15]
• Solubility: Slightly soluble in Chloroform and Ethyl Acetate.[15] For formulation, protocols using solvents like DMSO, PEG300, and Tween-80 have been developed to achieve concentrations suitable for administration.[18]
• Drug-Likeness and Lipophilicity: Calculated properties indicate that Irofulven possesses a favorable profile for a small molecule drug candidate.
• AlogP (Partition Coefficient): 1.67 [17]
• Polar Surface Area (PSA): 57.53 A˚2 [17]
• Hydrogen Bond Donors: 2 [17]
• Hydrogen Bond Acceptors: 3 [17]
• Lipinski's Rule of Five Violations: 0 [17]

The compliance with Lipinski's Rule of Five is a significant feature. These rules predict that a compound is likely to have good absorption and permeation characteristics if it meets certain criteria (molecular weight < 500 Da, AlogP < 5, H-bond donors < 5, H-bond acceptors < 10). Irofulven's favorable profile in this regard suggests inherent "developability" and likely contributed to the initial strong interest in advancing it into clinical trials, despite the high toxicity of its natural precursor.[17]

1.3 Pharmacological and Chemical Classification

Irofulven is classified based on both its therapeutic application and its chemical structure.

• Pharmacological Categories:
• Antineoplastic Agents [10]
• Antineoplastic Agents, Alkylating [10]
• Radiation-Sensitizing Agents [10]
• DNA Synthesis Inhibitors [12]
• Apoptosis Stimulants [12]
• Chemical Taxonomy:
• Kingdom: Organic compounds [10]
• Super Class: Terpenes [10]
• Class: Sesquiterpenes [6]
• Direct Parent: Cyclohexenones. The molecule contains a cyclohexenone moiety, which is a six-membered aliphatic ring with a ketone and one endocyclic double bond. This α,β-unsaturated ketone is a critical functional group for its biological activity.[10]

The following table consolidates the key identifiers and physicochemical properties of Irofulven into a single reference.

Table 1: Irofulven - Key Identifiers and Physicochemical Properties

Category	Property	Value	Source(s)
Identifiers	Generic Name	Irofulven	10
	IUPAC Name	(5'R)-5'-hydroxy-1'-(hydroxymethyl)-2',5',7'-trimethylspiro[cyclopropane-1,6'-indene]-4'-one	1
	CAS Number	158440-71-2	1
	DrugBank ID	DB05786	1
	ChEMBL ID	CHEMBL118218	1
	UNII	6B799IH05A	1
Chemical Formula & Weight	Molecular Formula	C15​H18​O3​	1
	Molecular Weight	246.31 g/mol	16
Structural Descriptors	SMILES	CC1=C(C2=C(C3(CC3)[C@@](C(=O)C2=C1)(C)O)C)CO	1
	InChIKey	NICJCIQSJJKZAH-AWEZNQCLSA-N	1
Physical Properties	Appearance	Orange Solid	15
	Melting Point	127-129 °C	15
	Solubility	Slightly soluble in Chloroform, Ethyl Acetate	15
Drug-Likeness Properties	AlogP	1.67	17
	Polar Surface Area	57.53 A˚2	17
	H-Bond Donors (Lipinski)	2	17
	H-Bond Acceptors (Lipinski)	3	17
	Rule of 5 Violations (Lipinski)	0	17

Section 2: Origin and Synthesis

The history of Irofulven is inextricably linked to its natural product origins, representing a classic example of leveraging natural toxins for therapeutic development through chemical modification.

2.1 The Natural Precursor: Illudin S and the Jack O'Lantern Mushroom

Irofulven is a semisynthetic derivative of illudin S, a toxic sesquiterpene metabolite that belongs to a family of compounds known as illudins.[1] The natural source of illudin S is the poisonous and strikingly bioluminescent fungus

Omphalotus illudens, colloquially named the Jack O'Lantern mushroom.[1] The illudins were first isolated over five decades ago and were subsequently found to possess a broad spectrum of biological activities, including antibacterial, antiviral, and potent antitumor properties.[2]

However, the direct therapeutic application of illudin S was precluded by its profound systemic toxicity and consequently low therapeutic index.[2] Preclinical studies in animal models revealed indiscriminate cytotoxicity, raising significant safety concerns that halted its development as a clinical candidate.[5] This fundamental challenge—the need to separate the desirable antitumor efficacy from the unacceptable host toxicity—was the primary driver for the chemical research that ultimately led to Irofulven.

2.2 Semi-Synthetic Derivation and Total Synthesis of Irofulven

The development of Irofulven was a deliberate and successful medicinal chemistry effort to engineer an illudin S analog with a superior therapeutic profile. The goal was to create a molecule that was significantly less toxic than the parent compound while retaining, or even enhancing, its potent and selective antitumor activity.[2] This effort led to the creation of a new family of compounds known as acylfulvenes. Acylfulvenes are derived from illudin S through a key chemical transformation known as a reverse Prins reaction, which is typically acid-catalyzed.[2] A more specific protocol for converting illudin S to Irofulven (hydroxymethylacylfulvene) involves treatment with excess acid, such as sulfuric acid (

H2​SO4​), in the presence of formaldehyde (CH2​O).[21] This modification fundamentally alters the reactivity of the molecule, reducing its indiscriminate cytotoxicity by nearly two orders of magnitude compared to illudin S.[5]

While this semi-synthetic approach was foundational, it relied on the production of the illudin S starting material from fungal fermentation cultures. This biological production method presented significant logistical and safety challenges, including low and variable expression yields, long culture times (often exceeding four weeks), contamination with the related compound illudin M, and the inherent biohazard associated with handling large quantities of a highly toxic substance.[22] These manufacturing hurdles provided a strong impetus for the development of

de novo total chemical synthesis routes that could produce Irofulven and other acylfulvenes without relying on the natural product precursor. A total synthesis of (±)-hydroxymethylacylfulvene has been reported, proceeding in 14 steps from simpler, commercially available starting materials.[20] The advancement from semi-synthesis to total synthesis represents a critical step toward making this drug class commercially viable. It de-risks the manufacturing supply chain from the variability and hazards of fermentation, enabling the scalable, reproducible, and controlled production required for late-stage clinical trials and potential commercialization. This ongoing innovation is reflected in recent patent filings by Lantern Pharma, which describe novel synthetic pathways for Irofulven and a new generation of illudin analogs, signaling a continued commitment to the chemical optimization of this promising class of anticancer agents.[22]

Section 3: Preclinical Pharmacology and Mechanism of Action

The antitumor effect of Irofulven is governed by a unique and multi-step mechanism of action that distinguishes it from conventional chemotherapeutic agents. Its efficacy is dependent on specific intracellular enzymatic activation, the induction of a distinct form of DNA damage, and the exploitation of specific deficiencies in cellular DNA repair machinery.

3.1 Bioactivation and Molecular Targeting

Irofulven is a prodrug, meaning it is administered in an inactive form and requires metabolic conversion within the cell to become cytotoxic.[5] This critical bioactivation step is catalyzed by an NADPH-dependent alkenal/one oxidoreductase (AOR).[1] This enzyme is also identified in the literature as Prostaglandin Reductase 1 (PTGR1).[25] The enzymatic reduction of the

α,β-unsaturated ketone on the cyclohexenone ring of Irofulven is believed to unmask the inherent electrophilicity of its strained cyclopropyl group, transforming the molecule into a highly reactive intermediate.[5]

The level of AOR/PTGR1 activity within cancer cells is a primary determinant of their sensitivity to Irofulven. Studies have demonstrated a strong positive correlation between AOR enzyme activity and the growth inhibitory effects of the drug across a panel of human tumor cell lines.[7] This establishes AOR/PTGR1 expression as a key predictive biomarker for Irofulven efficacy. Once activated, this unstable electrophilic intermediate rapidly and covalently binds to cellular nucleophiles, primarily targeting macromolecules such as DNA and proteins to form stable adducts.[1] It is the formation of these adducts, particularly on DNA, that initiates the cascade of events leading to cell death.

3.2 DNA Damage and Cellular Response

As an alkylating agent, the principal cytotoxic effect of Irofulven is the induction of DNA damage.[1] The activated form of the drug covalently binds to DNA, with a preference for purine bases like adenine, forming Irofulven-DNA adducts.[15] This direct modification of the DNA structure physically obstructs critical cellular processes. The presence of these bulky adducts on the DNA template leads to a potent inhibition of DNA replication and synthesis, as the replication machinery cannot proceed past the lesions.[4]

The disruption of DNA replication triggers cell cycle checkpoint mechanisms, causing cells to arrest primarily in the S-phase of the cell cycle.[1] This arrest provides the cell with an opportunity to repair the DNA damage. However, the nature of the Irofulven-induced lesions is such that they are often irreparable, particularly in certain genetic contexts. The persistence of this damage serves as a potent signal for the initiation of programmed cell death, or apoptosis.[4] The apoptotic cascade triggered by Irofulven has been shown to involve the activation of the ATM-dependent CHK2 kinase pathway in response to DNA damage, as well as the activation of downstream executioner caspases.[8]

3.3 Interaction with DNA Repair Pathways: The Nucleotide Excision Repair (NER) Axis

A defining feature of Irofulven's mechanism lies in its unique interaction with the cell's DNA repair systems. While conventional alkylating agents like cisplatin create inter- and intrastrand DNA cross-links that are recognized and repaired by multiple pathways, Irofulven induces a distinct type of DNA lesion. These Irofulven-DNA adducts are largely ignored by the global genome repair (GG-NER) sub-pathway, which is responsible for scanning the entire genome for damage.[13]

Instead, the repair of Irofulven-induced damage is almost exclusively dependent on the transcription-coupled NER (TC-NER) sub-pathway.[13] TC-NER is a specialized process that specifically removes DNA lesions from the transcribed strand of active genes. It is initiated when the RNA polymerase II enzyme physically stalls at the site of a DNA adduct during the process of gene transcription. This stalling event recruits the TC-NER machinery, including key proteins encoded by genes such as

ERCC2 (XPD) and ERCC3 (XPB), to the site of the lesion to initiate repair.[4]

This exclusive reliance on TC-NER for repair creates a powerful therapeutic opportunity known as synthetic lethality. Cancer cells that have a pre-existing genetic deficiency in the TC-NER pathway are incapable of repairing the DNA damage caused by Irofulven. In these cells, the stalled transcription complexes cannot be resolved, leading to persistent DNA damage signaling, replication fork collapse, and ultimately, cell death. In contrast, normal, non-cancerous cells with a functional TC-NER pathway can efficiently repair the damage and survive.[4] This differential effect creates a potentially large therapeutic window, allowing Irofulven to selectively kill cancer cells with specific DNA repair defects while sparing normal tissues. This discovery is the cornerstone of the modern, biomarker-driven strategy for Irofulven, which aims to select patients whose tumors harbor deficiencies in TC-NER genes, thereby predicting hypersensitivity to the drug.

3.4 Evasion of Common Resistance Mechanisms

Further enhancing its therapeutic potential, Irofulven's efficacy is notably unaffected by several of the most common mechanisms through which cancer cells develop resistance to chemotherapy.

• p53 Tumor Suppressor Status: The p53 protein is a master regulator of the cell cycle and apoptosis, and its mutation or loss is a frequent event in cancer that often confers resistance to DNA-damaging agents. Irofulven, however, retains its cytotoxicity in cancer cells regardless of their p53 status—it is effective in cells that are p53-wild-type, p53-mutated, or p53-null.[1] While the specific cell cycle arrest point may differ (p53 wild-type cells tend to arrest at the G1/S checkpoint, whereas p53-mutant cells arrest later in S and G2/M), both ultimately proceed to apoptosis, indicating that Irofulven can bypass this common resistance axis.[18]
• Multidrug Resistance (MDR) Efflux Pumps: Many cancers become resistant to chemotherapy by overexpressing transmembrane pumps, such as P-glycoprotein (encoded by the MDR1 gene) and Multidrug Resistance-associated Protein 1 (MRP1), which actively eject drugs from the cell. Irofulven is not a substrate for these major efflux pumps. Consequently, it can accumulate to cytotoxic concentrations and remain effective even in tumors that have developed broad resistance to a wide range of other chemotherapeutic agents.[1]
• Mismatch Repair (MMR) Status: The mismatch repair system is another DNA repair pathway, and its deficiency can affect cellular responses to certain drugs. The cytotoxic activity of Irofulven has been shown to be independent of the cell's MMR function.[9]

This ability to circumvent multiple, clinically significant resistance pathways makes Irofulven a particularly attractive agent for treating advanced, refractory cancers that have failed prior lines of therapy. The drug's mechanism suggests a dual-biomarker strategy for maximizing its clinical benefit: the ideal patient would have a tumor characterized by both high expression of the activating enzyme AOR/PTGR1 (ensuring the prodrug is converted to its active form) and a deficiency in the TC-NER pathway (ensuring the resulting DNA damage is lethal). This sophisticated, mechanistically-grounded approach to patient selection explains the failures of early trials in unselected populations and illuminates the path forward for its successful clinical development.

Section 4: Pharmacokinetics and Metabolism (ADME Profile)

The disposition of Irofulven within the human body is characterized by rapid clearance of the parent compound, extensive metabolism into numerous derivatives, and a primary reliance on renal excretion. Understanding its Absorption, Distribution, Metabolism, and Excretion (ADME) profile is critical for interpreting its clinical activity and toxicity.

4.1 Absorption and Distribution

As an investigational agent, Irofulven has been administered clinically via intravenous (IV) infusion, typically over a short duration of 5 to 30 minutes.[32] This route ensures complete bioavailability of the administered dose into the systemic circulation.

Preclinical studies using radiolabeled Irofulven in animal models have indicated that the drug undergoes rapid and wide tissue distribution following administration. The highest concentrations of drug-related material were observed in key organs of metabolism and excretion, including the liver and kidneys, as well as the stomach and adrenal glands.[33] In human plasma, Irofulven exhibits moderate binding to plasma proteins, with bound fractions reported to be in the range of 55% to 63%.[33] This level of binding leaves a substantial fraction of the drug free to distribute into tissues and exert its pharmacological effects.

4.2 Metabolism

Irofulven is a prodrug that undergoes rapid and extensive metabolism, to the extent that the parent compound is virtually undetectable in plasma shortly after administration.[32] The metabolic profile is complex and central to both its efficacy and its elimination.

The primary and most crucial metabolic step is the bioactivation pathway catalyzed by NADPH-dependent alkenal/one oxidoreductase (AOR/PTGR1), which converts Irofulven into its cytotoxic form.[1] Beyond this initial activation, the drug is subject to further biotransformation. A pivotal human study utilizing radiolabeled [¹⁴C]irofulven was able to track the fate of the molecule and its derivatives. This study identified a total of twelve distinct metabolites in human plasma and urine samples.[34] Among the structurally characterized metabolites were a cyclopropane ring-opened product (designated M2), indicating cleavage of the key reactive moiety, as well as several Phase II conjugation products. These included multiple glucuronide and glutathione conjugates, which are typical products of detoxification pathways that increase the water solubility of xenobiotics to facilitate their excretion.[34]

4.3 Excretion

The elimination of Irofulven and its numerous metabolites from the body occurs predominantly through the kidneys. The human radiolabel study provided definitive evidence for this route of excretion. Over a period of 144 hours following a single IV infusion of [¹⁴C]irofulven, a mean of 71.2% of the administered radioactivity was recovered in the urine.[34] In contrast, fecal excretion accounted for only a minor fraction of the dose, with a mean of 2.9% recovered via this route.[34] Notably, no unchanged parent Irofulven was detected in urine samples, confirming that the drug is completely metabolized before its elimination.[35] This heavy reliance on renal clearance for the vast majority of the drug's metabolites directly explains why renal dysfunction emerged as a principal dose-limiting toxicity in clinical trials. The kidneys are exposed to the highest concentrations of these metabolites for the longest duration, making them a primary site of potential toxicity.

4.4 Pharmacokinetic Parameters

The pharmacokinetic parameters of Irofulven reveal a stark and highly significant contrast between the disposition of the parent drug and its metabolites.

• Half-life: The parent Irofulven molecule is characterized by an extremely short elimination half-life (t1/2​), with reported values ranging from 2 to 10 minutes [33] and a mean value of 4.91 minutes in one study.[32] This reflects its rapid conversion into metabolites. In dramatic contrast, the terminal half-life of total drug-related radioactivity (representing the pool of all metabolites) is exceptionally long, with a mean of 116.5 hours.[34]
• Clearance: Consistent with its short half-life, the parent drug exhibits very high plasma clearance. One Phase I study reported a mean clearance of 4.57 L/min/m².[32]
• Dose Proportionality: The pharmacokinetics of Irofulven are linear and predictable within the clinically tested dose range. Studies have demonstrated dose-proportional increases in both the maximum plasma concentration (Cmax​) and the total systemic exposure (area under the concentration-time curve, AUC).[33]

The profound disparity between the half-life of the parent drug (minutes) and its metabolites (days) is a critical pharmacokinetic feature. This "hit-and-run" mechanism implies that the initial DNA damage is inflicted rapidly by the unstable active metabolite, but the resulting DNA adducts and stable circulating metabolites persist in the body for an extended period. This long persistence of drug-related material could be responsible for the delayed-onset toxicities, such as myelosuppression and renal dysfunction, observed in clinical trials. It also provides a strong pharmacokinetic rationale for the use of intermittent dosing schedules (e.g., weekly or bi-weekly), which allow time for the long-term biological effects of the previous dose to manifest and for the patient to recover before the next administration.

Section 5: Clinical Development and Efficacy

The clinical development of Irofulven has followed a complex and challenging path, characterized by initial high hopes, followed by modest results in broad populations that led to a period of dormancy, and a recent revival fueled by a modern, biomarker-driven precision medicine approach.

5.1 Overview of Clinical Journey and Regulatory Status

Irofulven was originally synthesized and patented by researchers at the University of California, San Diego (UCSD).[11] The promising preclinical data led to its licensing to MGI PHARMA, Inc., which spearheaded its initial clinical development.[1] The drug's novel mechanism and potent activity in xenograft models generated significant optimism, culminating in the FDA granting it "fast track" status in 2001 to expedite its review for deadly malignancies like pancreatic cancer.[1]

However, the subsequent Phase II and III trials conducted in the early 2000s, which enrolled patients largely unselected for molecular biomarkers, yielded disappointing results. While some activity was observed, the efficacy was often modest and not statistically significant enough to support regulatory approval, particularly in light of the drug's considerable toxicity profile.[11] Following the acquisition of MGI Pharma by Eisai, development slowed, and the drug was eventually considered "previously abandoned".[11] The rights were later returned to UCSD and subsequently licensed to smaller biotech companies, including Lantern Pharma and Allarty Therapeutics, which have championed its revival.[11] This new phase of development is predicated entirely on a biomarker-driven strategy, aiming to use predictive diagnostics to select patients with TC-NER deficiencies who are most likely to derive substantial benefit from the drug, thereby transforming its risk-benefit profile.

The following table provides a summary of major clinical trials that have defined the development history of Irofulven across various cancer types.

Table 2: Summary of Major Clinical Trials of Irofulven

Indication	Phase	Trial Identifier	Regimen	Key Outcome	Source(s)
Ovarian Cancer	II	GOG-129L (NCT00005031)	Monotherapy	PR: 12.7%; SD: 54.6%; Median PFS: 6.4 mo	14
Prostate Cancer (HRPC)	II	N/A	Monotherapy	PR: 13%; SD: 84%; Median PFS: 3.2 mo	40
Prostate Cancer (Docetaxel-Resistant)	II	N/A	IROF/Prednisone vs. IROF/Cape/Pred vs. Mito/Pred	Median OS: 10.1 / 9.5 / 7.4 mo	41
Prostate Cancer (mCRPC)	II	NCT03643107	IROF/Prednisone (Biomarker-selected)	Ongoing evaluation of response rate in DRP®-positive patients	43
Pancreatic Cancer (Stage III/IV)	II	NCT00003760	Monotherapy	Phase II trial completed; results not detailed in sources	45
Pancreatic Cancer (Refractory)	I	N/A	Monotherapy	One durable PR (7 months) observed	47
Renal Cell Carcinoma (Advanced)	II	N/A	Monotherapy	No objective responses observed	48
NSCLC (Relapsed/Refractory)	II	CALGB 39805 (NCT00003666)	Monotherapy	Phase II trial completed	50
Advanced Solid Tumors	I-II	NCT00374660	IROF + Oxaliplatin	MTD and safety evaluation	51

5.2 Clinical Trials in Ovarian Cancer

Irofulven was extensively investigated as a potential treatment for recurrent or persistent ovarian cancer, given strong preclinical signals.[11] A key multicenter Phase II trial was conducted by the Gynecologic Oncology Group (GOG) in patients with intermediately platinum-sensitive disease (recurrence 6-12 months after platinum therapy).[14] This study employed an intermittent dosing schedule (0.45 mg/kg IV on days 1 and 8 of a 21-day cycle) designed to be more tolerable than earlier daily regimens. Among 55 evaluable patients, the trial demonstrated a partial response (PR) rate of 12.7% and stable disease (SD) in an additional 54.6% of patients. The median progression-free survival (PFS) was 6.4 months, and the median overall survival (OS) was a promising 22.1+ months.[14] While the regimen was well-tolerated, the investigators concluded that Irofulven demonstrated only "modest activity" as a single agent in this unselected population.[39] The general consensus was that its future in ovarian cancer, if any, would likely be in combination with other agents, such as PARP inhibitors or platinum drugs, particularly in a biomarker-selected setting where NER deficiency is more prevalent.

5.3 Clinical Trials in Prostate Cancer

Prostate cancer, particularly advanced, castration-resistant prostate cancer (CRPC), has been one of the most promising indications for Irofulven.[43] An early Phase II single-agent trial in 42 chemotherapy-naïve patients with metastatic hormone-refractory prostate cancer (HRPC) showed a PR rate of 13% and a disease stabilization rate of 84%.[40] The median PFS was 3.2 months, providing a clear signal of clinical activity.[40]

More significantly, a randomized Phase II study was conducted in patients with HRPC who had already progressed on docetaxel-based chemotherapy, a setting with very poor prognosis.[41] The trial compared two Irofulven-containing arms (Irofulven plus prednisone; Irofulven plus capecitabine and prednisone) against a standard-of-care comparator arm (mitoxantrone plus prednisone). The results were highly encouraging, showing that both Irofulven regimens led to longer median overall survival (10.1 months and 9.5 months) compared to the mitoxantrone arm (7.4 months). The Irofulven arms also demonstrated superior PSA response rates and longer time to progression, leading the investigators to conclude that a larger randomized trial was warranted.[42] This trial was pivotal in establishing Irofulven's potential in a heavily pre-treated, resistant patient population. This promise is now being pursued with a precision medicine lens in an ongoing Phase II trial (NCT03643107), which is prospectively using a proprietary Drug Response Predictor (DRP®) biomarker to select patients with metastatic CRPC who are most likely to benefit from Irofulven therapy.[43]

5.4 Clinical Trials in Pancreatic Cancer

Pancreatic cancer was one of the first indications for which Irofulven showed significant promise, leading to its "fast track" designation.[1] Objective responses were reported in early clinical studies, including in patients with gemcitabine-refractory disease, a notoriously difficult-to-treat condition.[8] A Phase I study of Irofulven using a daily-times-five schedule documented a durable partial response lasting 7 months in a patient with advanced, refractory metastatic pancreatic cancer, providing a strong early signal of efficacy.[47]

These promising early results were supported by robust preclinical data. In xenograft models using the MiaPaCa human pancreatic cancer cell line, Irofulven demonstrated curative activity, and its antitumor effect was enhanced when combined with gemcitabine.[8] This led to the initiation of a Phase II trial (NCT00003760) for patients with unresectable Stage III or IV pancreatic cancer.[45] Development for this indication progressed as far as Phase III clinical trials, but these were ultimately discontinued, likely due to a combination of modest efficacy in an unselected population and significant toxicity.[1]

5.5 Investigations in Other Malignancies

Irofulven has been evaluated across a range of other solid tumors, with mixed results.

• Renal Cell Carcinoma (RCC): Despite some disease stabilizations noted in Phase I, dedicated Phase II trials of Irofulven in patients with advanced RCC were uniformly negative. No objective responses were observed, and the drug was deemed to have no meaningful single-agent activity in this malignancy at the dose and schedule tested.[48]
• Non-Small Cell Lung Cancer (NSCLC): A Phase II trial (CALGB 39805, registered as NCT00003666) was sponsored by the Alliance for Clinical Trials in Oncology to evaluate Irofulven's effectiveness in patients with relapsed or refractory NSCLC.[50]
• Advanced Solid Tumors and Combination Studies: Several Phase I and II trials have explored Irofulven's safety and efficacy in patients with a variety of advanced solid tumors, often in combination with other cytotoxic agents. Studies have evaluated its use with cisplatin [11] and oxaliplatin (NCT00374660) [30], with preclinical data suggesting synergistic interactions. Additionally, its activity was assessed in a panel of pediatric solid tumor xenografts, where it showed high sensitivity, though the systemic exposure required for tumor regression was noted to be in excess of what was tolerable in human patients with the schedules used.[4]

Section 6: Safety, Tolerability, and Toxicology

The clinical utility of Irofulven is significantly constrained by its toxicity profile and narrow therapeutic window. A comprehensive understanding of its adverse effects is essential for managing patients and for the rational design of safer dosing regimens and combination therapies.

6.1 Dose-Limiting Toxicities (DLTs)

Across numerous Phase I and II clinical trials, a consistent pattern of dose-limiting toxicities has emerged, defining the maximum tolerated dose (MTD) of the drug.

• Myelosuppression: Hematologic toxicity is a primary and consistent DLT. This most frequently manifests as delayed-onset and often persistent thrombocytopenia (a clinically significant decrease in platelet count) and neutropenia (a decrease in infection-fighting neutrophils).[33] In some studies, Grade 4 (severe) neutropenia and thrombocytopenia were observed, sometimes leading to treatment delays or dose reductions.[36]
• Renal Dysfunction: The second major DLT is renal toxicity. At higher dose levels, particularly with daily dosing schedules, patients have developed renal dysfunction, which can present as a form of renal tubular acidosis.[33] This toxicity is mechanistically linked to the drug's primary route of elimination via the kidneys. It was noted in a Phase I trial that the incidence of renal toxicity could be ameliorated by the use of prophylactic intravenous hydration, a strategy to dilute the concentration of toxic metabolites in the renal tubules.[47]

6.2 Common and Notable Adverse Events

Beyond the dose-limiting toxicities, Irofulven is associated with a range of other common adverse events.

• Gastrointestinal Effects: Nausea and vomiting are highly prevalent, with Irofulven being described as "highly emetogenic".[32] Other common GI side effects include anorexia (loss of appetite) and diarrhea. While frequent, these effects are typically mild to moderate (Grade 1 or 2) and can be managed with standard supportive care.[32]
• Constitutional Symptoms: Fatigue, also referred to as asthenia, is a very common and prominent toxicity reported by patients receiving Irofulven.[32]
• Ocular Toxicity: A unique and clinically significant adverse effect associated with Irofulven is a dose-dependent retinal toxicity that specifically affects cone photoreceptors.[39] Patients experiencing this toxicity reported symptoms such as photophobia (light sensitivity), reduced vision in bright light, and altered color perception.[54] Ophthalmologic examinations and electroretinography confirmed cone dysfunction with relative sparing of rod function. Histopathology from one patient revealed a reduction in the number of cone cells.[54] Crucially, this toxicity was found to be more closely correlated with the peak plasma concentration (i.e., the dose per infusion) than with the cumulative dose. This finding directly led to the implementation of dose caps (e.g., a maximum of 50 mg per infusion) and the shift toward more intermittent schedules with lower individual doses to mitigate this risk.[39]
• Other Toxicities: Facial erythema (flushing) has been commonly reported during or after infusion.[36] Additionally, at least one case of a severe (Grade 3) skin injury following extravasation (leakage of the drug outside the vein) has been reported, indicating that Irofulven should be considered a vesicant and handled with appropriate care during administration.[32]

The following table summarizes the key adverse events associated with Irofulven treatment.

Table 3: Safety Profile of Irofulven - Common and Dose-Limiting Toxicities

System Organ Class	Adverse Event	Severity/Frequency	Management Notes	Source(s)
Hematologic	Thrombocytopenia	DLT; Common Grade 3/4	Dose-limiting, may be persistent and require treatment delay/dose reduction.	33
	Neutropenia	DLT; Common Grade 3/4	Dose-limiting, may be associated with febrile neutropenia.	36
Renal	Renal Dysfunction / Tubular Acidosis	DLT; Occurs at higher doses	Prophylactic IV hydration may ameliorate. Requires monitoring of renal function.	33
Gastrointestinal	Nausea / Vomiting	Very Common; Highly emetogenic	Typically Grade 1/2. Requires standard antiemetic prophylaxis.	32
	Anorexia (Loss of Appetite)	Common	Contributes to fatigue and weight loss.	32
	Diarrhea	Common	Typically Grade 1/2.	41
Constitutional	Fatigue / Asthenia	Very Common	Can be a prominent and debilitating side effect.	32
Ocular	Retinal Cone Dysfunction	Dose-dependent; Can be severe	Symptoms include photophobia, altered color vision. Mitigated by lower dose per infusion and dose caps.	39
Dermatologic/Local	Facial Erythema	Common	Flushing reaction during or after infusion.	36
	Extravasation Injury	Rare but severe	Vesicant properties; requires careful IV administration.	32

6.3 Drug-Drug Interactions

The potential for drug-drug interactions with Irofulven has been evaluated both pharmacokinetically and pharmacodynamically.

• Pharmacokinetic Interactions: In a European Phase I study combining Irofulven with cisplatin, no evidence of pharmacokinetic drug-drug interactions was observed, suggesting that co-administration does not significantly alter the clearance of either agent.[11]
• Pharmacodynamic Interactions: Several potential pharmacodynamic interactions have been identified.
• Methemoglobinemia: There is an increased risk of developing methemoglobinemia, a condition where hemoglobin is unable to effectively release oxygen to body tissues, when Irofulven is combined with a wide range of local anesthetics (e.g., benzocaine, lidocaine, bupivacaine) and other compounds such as phenol.[10]
• Thrombosis: The risk of thrombotic events may be increased when Irofulven is co-administered with erythropoiesis-stimulating agents like darbepoetin alfa and erythropoietin, which are often used to manage anemia in cancer patients.[10]

Section 7: Conclusion and Future Directions

The extensive research and clinical development history of Irofulven provides a compelling narrative of a drug's journey from a natural toxin to a potential precision medicine. Its trajectory encapsulates key trends in oncology drug development, highlighting the limitations of the "one-size-fits-all" approach and the transformative power of biomarker discovery.

7.1 Synthesis of Findings: Irofulven as a Paradigmatic Case

Irofulven's story is a paradigm of modern drug development. It began with the rational chemical modification of a potent but unacceptably toxic fungal metabolite, illudin S, to create a compound with a more favorable therapeutic index. Its unique mechanism of action—requiring enzymatic bioactivation to form novel DNA lesions that are selectively repaired by the TC-NER pathway—sets it apart from all conventional alkylating agents. Furthermore, its ability to bypass common resistance mechanisms like p53 mutation and MDR1-mediated efflux positioned it as a promising agent for refractory cancers.

However, its challenging safety profile, defined by dose-limiting myelosuppression and renal toxicity, created a narrow therapeutic window. When tested in broad, molecularly unselected patient populations, its clinical benefit was often modest and insufficient to outweigh its risks. This led to its status as a "failed" or "abandoned" drug. The critical turning point was the elucidation of its precise interaction with the DNA repair machinery, which revealed that its cytotoxicity is massively amplified in cells with TC-NER deficiency. This discovery has resurrected Irofulven, reframing it not as a broad-spectrum cytotoxic agent, but as a highly targeted drug for a specific, identifiable molecular subtype of cancer.

7.2 The Critical Role of Predictive Biomarkers

The entire future of Irofulven as a therapeutic agent is contingent upon the successful clinical validation of a dual-biomarker strategy to select patients most likely to benefit.

• Transcription-Coupled NER (TC-NER) Deficiency: The primary and most critical biomarker for patient selection is a functional defect in the TC-NER pathway. Tumors with mutations in key TC-NER genes, such as ERCC2 and ERCC3, are unable to repair the specific DNA adducts created by Irofulven, leading to a synthetic lethal interaction and profound drug sensitivity.[4] Genomic sequencing to identify these mutations is therefore the key patient selection tool.
• AOR/PTGR1 Expression: A necessary secondary condition for efficacy is the presence of the activating enzyme, AOR/PTGR1, within the tumor cells. High expression of this enzyme is required to efficiently convert the Irofulven prodrug into its active, DNA-damaging form.[7] Tumors with low or absent AOR/PTGR1 expression would be predicted to be resistant, even if they harbor a TC-NER defect.

Therefore, the optimal clinical strategy involves a two-gate screening process: identifying patients whose tumors are both AOR/PTGR1-positive (to ensure the drug is "switched on") and TC-NER-deficient (to ensure the resulting damage is lethal).

7.3 Future Clinical and Research Trajectory

The path forward for Irofulven is now clearly defined and centers on precision oncology principles.

• Biomarker-Driven Clinical Trials: The immediate and most critical step is the successful execution of prospective, biomarker-driven clinical trials. The ongoing study in metastatic castration-resistant prostate cancer (NCT03643107), which uses a diagnostic to select patients, is a template for all future development.[44] Success in this and similar trials is essential to definitively prove that the biomarker strategy can translate the drug's potent preclinical activity into substantial clinical benefit.
• Expansion to Other Indications: Future research should focus on identifying other malignancies that have a high prevalence of the dual-biomarker signature. Comprehensive genomic and transcriptomic analysis of various tumor types could pinpoint new indications where Irofulven is likely to be highly effective.
• Rational Combination Therapies: The unique mechanism of Irofulven makes it an ideal candidate for rational combination therapies. Preclinical data has already demonstrated strong synergy with platinum-based agents (cisplatin, oxaliplatin), whose DNA cross-links are repaired by different NER sub-pathways, potentially overwhelming the cell's repair capacity.[29] An even more compelling future direction is to combine Irofulven with PARP inhibitors. In tumors with TC-NER deficiency, Irofulven creates single-strand breaks and stalled replication forks, which PARP inhibitors are designed to exploit, potentially leading to profound synergistic cell killing.
• Next-Generation Acylfulvenes: The ongoing development of new acylfulvene analogs, as evidenced by recent patent activity, represents a parallel path forward.[24] This research aims to synthesize second- and third-generation compounds that may possess an even wider therapeutic window, reduced toxicity, or altered activation requirements, potentially expanding the utility of this promising class of mushroom-derived anticancer agents.

Works cited

1. (-)-Irofulven | C15H18O3 | CID 148189 - PubChem, accessed September 19, 2025, https://pubchem.ncbi.nlm.nih.gov/compound/Irofulven
2. Irofulven – Halloween Trick or a Beacon of Light, accessed September 19, 2025, https://www.fungimag.com/spring-08-articles/7_Medicinal.pdf
3. Structure of irofulven and illudin S | Download Scientific Diagram - ResearchGate, accessed September 19, 2025, https://www.researchgate.net/figure/Structure-of-irofulven-and-illudin-S_fig1_5546414
4. Relation between Irofulven (MGI-114) Systemic Exposure and Tumor Response in Human Solid Tumor Xenografts1 - AACR Journals, accessed September 19, 2025, https://aacrjournals.org/clincancerres/article/8/9/3000/289257/Relation-between-Irofulven-MGI-114-Systemic
5. US20050176074A1 - Bioactivation of alkylating agents for cancer ..., accessed September 19, 2025, https://patents.google.com/patent/US20050176074A1/en
6. Definition of irofulven - NCI Drug Dictionary - NCI, accessed September 19, 2025, https://www.cancer.gov/publications/dictionaries/cancer-drug/def/irofulven
7. NADPH alkenal/one oxidoreductase activity determines sensitivity of cancer cells to the chemotherapeutic alkylating agent irofulven - PubMed, accessed September 19, 2025, https://pubmed.ncbi.nlm.nih.gov/14977853/
8. Activity of Irofulven against Human Pancreatic Carcinoma Cell Lines In Vitro and In Vivo - Anticancer Research, accessed September 19, 2025, https://ar.iiarjournals.org/content/anticanres/24/1/59.full-text.pdf
9. Marked Activity of Irofulven toward Human Carcinoma Cells - AACR Journals, accessed September 19, 2025, https://aacrjournals.org/clincancerres/article/9/7/2817/203594/Marked-Activity-of-Irofulven-toward-Human
10. Irofulven: Uses, Interactions, Mechanism of Action | DrugBank Online, accessed September 19, 2025, https://go.drugbank.com/drugs/DB05786
11. Irofulven - Wikipedia, accessed September 19, 2025, https://en.wikipedia.org/wiki/Irofulven
12. Irofulven - Lantern Pharma - AdisInsight - Springer, accessed September 19, 2025, https://adisinsight.springer.com/drugs/800006987
13. Anti-tumour compounds illudin S and Irofulven induce DNA lesions ignored by global repair and exclusively processed by transcription- and replication-coupled repair pathways - PubMed, accessed September 19, 2025, https://pubmed.ncbi.nlm.nih.gov/12531012/
14. A Phase 2 Evaluation of Irofulven as Second-line Treatment of Recurrent or Persistent Intermediately Platinum-Sensitive Ovarian or Primary Peritoneal Cancer A Gynecologic Oncology Group Trial - ResearchGate, accessed September 19, 2025, https://www.researchgate.net/publication/51053250_A_Phase_2_Evaluation_of_Irofulven_as_Second-line_Treatment_of_Recurrent_or_Persistent_Intermediately_Platinum-Sensitive_Ovarian_or_Primary_Peritoneal_Cancer_A_Gynecologic_Oncology_Group_Trial
15. CAS 158440-71-2 Irofulven - BOC Sciences, accessed September 19, 2025, https://www.bocsci.com/product/irofulven-cas-158440-71-2-59994.html
16. HY-14429-10mg by MedChemexpress LLC - Insight Biotechnology limited, accessed September 19, 2025, https://insightbio.com/productinfo/HY-14429-10mg/MedChemexpress%20LLC
17. Compound: IROFULVEN (CHEMBL118218) - ChEMBL - EMBL-EBI, accessed September 19, 2025, https://www.ebi.ac.uk/chembl/explore/compound/CHEMBL118218
18. (-)-Irofulven (MGI 114) | DNA Alkylating Agent - MedchemExpress.com, accessed September 19, 2025, https://www.medchemexpress.com/minus-irofulven.html
19. Activity of irofulven against human pancreatic carcinoma cell lines in ..., accessed September 19, 2025, https://pubmed.ncbi.nlm.nih.gov/15015576/
20. Total synthesis of hydroxymethylacylfulvene, an antitumour derivative of illudin S, accessed September 19, 2025, https://www.researchgate.net/publication/244537086_Total_synthesis_of_hydroxymethylacylfulvene_an_antitumour_derivative_of_illudin_S
21. Enantioselective Total Synthesis of (−)-Acylfulvene and ..., accessed September 19, 2025, https://pmc.ncbi.nlm.nih.gov/articles/PMC2805080/
22. US20210198191A1 - Illudin analogs, uses thereof, and methods for ..., accessed September 19, 2025, https://patents.google.com/patent/US20210198191A1/en
23. US11739043B2 - Illudin analogs, uses thereof, and methods for synthesizing the same - Google Patents, accessed September 19, 2025, https://patents.google.com/patent/US11739043B2/en
24. Patent Portfolio - Lantern Pharma Inc., accessed September 19, 2025, https://www.lanternpharma.com/about/patent-portfolio
25. LP-284, a small molecule acylfulvene, exerts potent antitumor activity in preclinical non-hodgkin's lymphoma models and in c - intoDNA, accessed September 19, 2025, https://intodna.com/wp-content/uploads/2024/06/Oncotarget-2023-Lantern-Pharma.pdf
26. Irofulven: Resurgence for alkylating therapy in cancer? - ResearchGate, accessed September 19, 2025, https://www.researchgate.net/publication/8089971_Irofulven_Resurgence_for_alkylating_therapy_in_cancer
27. go.drugbank.com, accessed September 19, 2025, https://go.drugbank.com/drugs/DB05786#:~:text=MGI%2D114(Irofulven)%20has,to%20DNA%20and%20protein%20targets.
28. Synergy of irofulven in combination with other DNA damaging agents: Synergistic interaction with altretamine, alkylating, and platinum-derived agents in the MV522 lung tumor model - ResearchGate, accessed September 19, 2025, https://www.researchgate.net/publication/5546414_Synergy_of_irofulven_in_combination_with_other_DNA_damaging_agents_Synergistic_interaction_with_altretamine_alkylating_and_platinum-derived_agents_in_the_MV522_lung_tumor_model
29. Synergy of irofulven in combination with other DNA damaging agents: synergistic interaction with altretamine, alkylating, and platinum-derived agents in the MV522 lung tumor model PMID: 18305940 | MedChemExpress, accessed September 19, 2025, https://www.medchemexpress.com/mce_publications/18305940.html
30. (PDF) Characterizations of irofulven cytotoxicity in combination with ..., accessed September 19, 2025, https://www.researchgate.net/publication/7684424_Characterizations_of_irofulven_cytotoxicity_in_combination_with_cisplatin_and_oxaliplatin_in_human_colon_breast_and_ovarian_cancer_cells
31. Phase I and Pharmacokinetic Study of Irofulven Administered Weekly or Biweekly in Advanced Solid Tumor Patients - AACR Journals, accessed September 19, 2025, https://aacrjournals.org/clincancerres/article/10/10/3377/182092/Phase-I-and-Pharmacokinetic-Study-of-Irofulven
32. Phase I clinical and pharmacokinetic trial of irofulven - PubMed, accessed September 19, 2025, https://pubmed.ncbi.nlm.nih.gov/11800027/
33. Phase I and Pharmacokinetic Study of Irofulven, a Novel Mushroom ..., accessed September 19, 2025, https://ascopubs.org/doi/10.1200/JCO.2000.18.24.4086
34. Pharmacokinetics, metabolism, and routes of excretion of ... - PubMed, accessed September 19, 2025, https://pubmed.ncbi.nlm.nih.gov/16896064/
35. HPLC/ESI-MS/MS chromatograms of irofulven (C) and its metabolites, GSH... | Download Scientific Diagram - ResearchGate, accessed September 19, 2025, https://www.researchgate.net/figure/HPLC-ESI-MS-MS-chromatograms-of-irofulven-C-and-its-metabolites-GSH-conjugate-A-and_fig2_6891211
36. Phase I and Pharmacokinetic Study of Irofulven, a Novel Mushroom-Derived Cytotoxin, Administered for Five Consecutive Days Every Four Weeks in Patients With Advanced Solid Malignancies - ResearchGate, accessed September 19, 2025, https://www.researchgate.net/publication/12211004_Phase_I_and_Pharmacokinetic_Study_of_Irofulven_a_Novel_Mushroom-Derived_Cytotoxin_Administered_for_Five_Consecutive_Days_Every_Four_Weeks_in_Patients_With_Advanced_Solid_Malignancies
37. ANTICANCER AGENTS FROM DIVERSE NATURAL SOURCES - University of Pretoria, accessed September 19, 2025, https://repository.up.ac.za/bitstreams/c8070630-5ea6-485d-974a-7b04d60400dc/download
38. Study Details | Irofulven in Treating Patients With Persistent or Recurrent, Refractory Endometrial Cancer | ClinicalTrials.gov, accessed September 19, 2025, https://clinicaltrials.gov/study/NCT00005031
39. A phase II evaluation of Irofulven (IND#55804, NSC#683863) as ..., accessed September 19, 2025, https://pmc.ncbi.nlm.nih.gov/articles/PMC3079178/
40. Irofulven demonstrates clinical activity against metastatic hormone ..., accessed September 19, 2025, https://pubmed.ncbi.nlm.nih.gov/15685033/
41. Randomized phase II trial of irofulven (IROF)/prednisone (P), IROF/capecitabine (C)/P or mitoxantrone (M)/P in docetaxel-pretreated hormone refractory prostate cancer (HRPC) patients (pts) | Journal of Clinical Oncology - ASCO Publications, accessed September 19, 2025, https://ascopubs.org/doi/10.1200/jco.2006.24.18_suppl.14513
42. Results of a randomized phase II study of irofulven in hormone-refractory prostate cancer patients that have failed first-line docetaxel treatment - ASCO Publications, accessed September 19, 2025, https://ascopubs.org/doi/10.1200/jco.2007.25.18_suppl.5068
43. Irofulven Completed Phase 2 Trials for Metastatic Castration Resistant Prostate Cancer Patients Treatment | DrugBank Online, accessed September 19, 2025, https://go.drugbank.com/drugs/DB05786/clinical_trials?conditions=DBCOND0061871&phase=2&purpose=treatment&status=completed
44. Study Details | NCT03643107 | Irofulven in AR-targeted and Docetaxel-Pretreated mCRPC Patients With Drug Response Predictor (DRP®), accessed September 19, 2025, https://clinicaltrials.gov/study/NCT03643107
45. Irofulven Completed Phase 2 Trials for Pancreatic Cancer Treatment | DrugBank Online, accessed September 19, 2025, https://go.drugbank.com/drugs/DB05786/clinical_trials?conditions=DBCOND0028482&phase=2&purpose=treatment&status=completed
46. Irofulvene In Treating Patients With Stage III Or Stage IV Pancreatic Cancer, accessed September 19, 2025, https://www.npcf.us/clinical-trials/irofulvene-in-treating-patients-with-stage-iii-or-stage-iv-pancreatic-cancer/
47. Phase I and Pharmacokinetic Study of Irofulven, a Novel Mushroom-Derived Cytotoxin, Administered for Five Consecutive Days Every Four Weeks in Patients With Advanced Solid Malignancies - PubMed, accessed September 19, 2025, https://pubmed.ncbi.nlm.nih.gov/11118470/
48. Phase II trial of irofulven (6-hydroxymethylacylfulvene) for patients with advanced renal cell carcinoma - PubMed, accessed September 19, 2025, https://pubmed.ncbi.nlm.nih.gov/11561691/
49. Irofulven, a novel inhibitor of DNA synthesis, in metastatic renal cell cancer - PubMed, accessed September 19, 2025, https://pubmed.ncbi.nlm.nih.gov/12448659/
50. Irofulven in Treating Patients With Relapsed or Refractory Non-small Cell Lung Cancer, accessed September 19, 2025, https://clinicaltrials.gov/study/NCT00003666
51. NCT00374660 | Study of Irofulven in Combination With Oxaliplatin in Patients With Advanced Solid Tumors | ClinicalTrials.gov, accessed September 19, 2025, https://clinicaltrials.gov/study/NCT00374660
52. Irofulven | CAS#158440-71-2 | antitumor agent | MedKoo, accessed September 19, 2025, https://www.medkoo.com/products/18886
53. Results of a randomized phase II study of irofulven in hormone-refractory prostate cancer patients that have failed first-line docetaxel treatment - ResearchGate, accessed September 19, 2025, https://www.researchgate.net/publication/339764143_Results_of_a_randomized_phase_II_study_of_irofulven_in_hormone-refractory_prostate_cancer_patients_that_have_failed_first-line_docetaxel_treatment
54. Retinal Cone Toxicity in an Ovarian Cancer Patient Treated with Irofulven | IOVS, accessed September 19, 2025, https://iovs.arvojournals.org/article.aspx?articleid=2412324
55. Synergy of irofulven in combination with other DNA damaging agents: synergistic interaction with altretamine, alkylating, and platinum-derived agents in the MV522 lung tumor model - PubMed, accessed September 19, 2025, https://pubmed.ncbi.nlm.nih.gov/18305940/
56. Abstract 751: Synthesis of irofulven analogs | Cancer Research - AACR Journals, accessed September 19, 2025, https://aacrjournals.org/cancerres/article/70/8_Supplement/751/566869/Abstract-751-Synthesis-of-irofulven-analogs