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2008 Bank of America Health Care Conference

May 2008

NASDAQ: ALTH

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Safe Harbor Statement

This presentation contains forward-looking statements that are made pursuant to the safe harbor provisions of the Private Securities Litigation Reform Act of 1995. Generally, you can identify these statements by the use of terms such as “may,” “will,” “should,” “expects,” “intends,” “plans,” anticipates,”“believes,” “estimates,” “predicts,” “projects,” “potential,” “continue,” and other similar terms or the negative of these terms, but their absence does not mean that a particular statement is not forward-looking. Forward-looking statements may include statements concerning: time lines for completing clinical trials; time lines for releasing data from clinical trials; time lines for initiating new clinical trials; our collaboration efforts; future licensing and acquisition activity; future product development activities; the expected safety and effectiveness of our product candidates in treating diseases; our competitive position; plans for regulatory filings; receipt of future regulatory approvals; our expected cash resources and requirements; plans for sales and marketing; implementation of corporate strategy; and other statements that are other than statements of historical facts. Such forward-looking statements are not guarantees of future performance and are subject to risks and uncertainties that may cause actual results to differ materially from those anticipated by the forward-looking statements. Additional information concerning the risks and uncertainties that may cause such differences is contained in the "Risk Factors" section of the Company's Annual Report on Form 10-K for the year ended December 31, 2007, and in the Company's other periodic reports and filings with the Securities and Exchange Commission. The Company cautions investors not to place undue reliance on the forward-looking statements contained in this presentation. All forward-looking statements are based on information currently available to the Company on the date hereof, and the Company undertakes no obligation to revise or update these forward-looking statements to reflect events or circumstances after the date of this presentation, except as required by law.

Note: The Allos logo is a trademark of Allos Therapeutics, Inc.

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Company HighlightsOncology-focused biopharmaceutical company

Prioritized, high-potential R&D pipeline with 2 proprietary candidates in development

PDX – unique antifolate with potential in hematologic malignancies and solid tumors

o 6 ongoing studies evaluating PDX in multiple indications

o SPA-approved pivotal Phase 2 trial in PTCL

RH1 – targeted chemotherapeutic prodrug

o Phase 1 study in advanced solid tumors & NHL ongoing

Business model focused on opportunities that can be addressed with a targeted sales and marketing organization

Experienced management team with proven results

Worldwide exclusive rights to both PDX and RH1

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Product Development Pipeline

Preclinical Phase 1 Phase 2 Phase 3 NDA MarketPDX

Peripheral T-cell Lymphoma

Additional Indication

Non-Hodgkin’s Lymphoma

B-cell Non-Hodgkin’s Lymphoma

PDX + Gemcitabine

Cutaneous T-cell Lymphoma

RH1

ongoing planned

Non-small Cell Lung Cancer

HEMATOLOGIC MALIGNANCIES

SOLID TUMORS

PROPEL: SPA approved, registration trial

Solid Tumors/NHL

(Phase 2)

(Phase 1/2)

(Phase 1/2a)

(Phase 1)

(Phase 2b)

(Phase 2)

(Phase 1)

PDX vs. Erlotinib

Non-small Cell Lung Cancer(Phase 1)

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PDX (pralatrexate): Unique AntifolateSmall molecule inhibitor of dihydrofolate reductase (DHFR), a key enzyme in folate metabolism and well-validated oncology target

Rationally designed for improved cancer cell uptake and retention

Superior preclinical profile compared to other folate analogs targeting DHFR

Clinical evidence of activity in T-cell malignancies and NSCLC

SPA-approved pivotal Phase 2 trial on-going in patients with relapsed or refractory PTCL

FDA Orphan Drug and Fast Track designation in patients with T- cell lymphoma

Mechanistic rationale for development in other oncology indications based on broad use of folate antagonists

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PDX: Mechanism of ActionSelectively Targets Folate Metabolism

FolateRFC-1

Folate

FH2FH4

DHFR

Methylene FH4

dUMP dTMP

ThymineThymidylate Synthase

DHFR

PDX

PDX

FPGS

PDX (Glun)

PDX is:

More potent than other DHFRinhibitors due to greater cell entry and retention

Efficient permeant

RFC-1 (transport)

Effective substrate

FPGS (polyglutamation)

Primarily targets

DHFR (pM affinity)Alimta, 5-FU, Tomudex target TS

Cell membrane

“Differential Activity And Potential Mechanism of Action of PDX, MTX, and Alimta in Human Cancer Models In Vivo and in Vitro” – 2007 AACR-NCI-EORTC:

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Disease Overview: NHL & PTCL

PTCL is an aggressive NHL subgroup with poor clinical prognosis

Peripheral T-Cell Lymphoma (PTCL)Non-Hodgkin’s Lymphoma (NHL)

2nd + line treatment

1st line treatment

Prognosis

Grade

Common Subtypes

Cell Origin

Definition

No labeled product or regimenNo standard 2nd line treatment

- Aggressive (+/-Rituxan)- ESHAP, ICE, DHAP (RR 30%-70%)

-Indolent- Rituxan, Zevalin (RR 47%-80%)

No labeled product or regimen- CHOP: 50-70% 1st line TRx response

rate, high relapse, short duration 4

CHOP + Rituxan- DLBCL (Aggressive): 2.9 yrs EFS3

- Follicular (Indolent): 2.4 yrs median PFS 3

- Worse than aggressive B-cell NHL - PTCL 5 yr OS = 25%2

- Better if NHL is of B-cell origin- DLBCL (intermed. risk) 5 yr OS = 49%1

AggressiveIndolent or aggressive

PTCL NOS (not otherwise specified) Angioimmunoblastic, Anaplastic large cell

Diffuse large B-cell, Follicular, Mantle, Burkitt

Mature T-cells (post-thymic)B-cell (85 - 90%) T-cell (10 -15%)

Aggressive subgroup of NHL (10 -15%)Diverse group of cancers originating in lymphatic system

1 Lossos et al., NEJM, 2004.; 2 Blood. 1997 Jun 1;89(11):3909-18; 3- Rituxan package insert; 4 Angelopoulou, M. et al., HAEMA, 2004

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Non-Hodgkin’s Lymphoma63,200

Precursor T-Cell1,600

Peripheral T-Cell6,300

Cutaneous TCL (Indolent)

1,000

Non-Cutaneous TCL(Aggressive)

5,000

T-Acute Lymphoblasticleukemia

T-Lymphoblastic Lymphoma

Peripheral TCL - Not otherwise specified

Anaplastic Large Cell Lymphoma (cutaneous)

Angioimmunoblastic TCL

NK/TCL Nasal

Mycosis Fungoides/Sezary Syndrome

Adult T-cell Leuk/Lymphoma (HTLV+)

T-cell granular Lymphocytic (indolent)**

Predominantly Leukemic300

Subcutaneous paniculitis-like TCL

Enteropathy typeIntestinal TCL

Hepatosplenic gamma-delta TCL

Anaplastic Large Cell Lymphoma (systemic) NK T-cell Leukemia

T-Cell Prolymphocytic Leukemia**

T-cell Lymphoma*7,900

B-Cell Lymphoma49,290

Transformed Mycosis Fungoides

Arranon: 3rd line T-ALL and T-LBL

Ontak, Zolinza, Targretin: 2nd line CTCL

PDX: 2nd line Aggressive PTCL

Source: “Aggressive Peripheral T-Cell Lymphomas” Hematology 2005, Savage, K. *12.5% (10 -15%) of NHL is T-cell ** Excluded from PROPEL

NHL Patient Population: T-Cell Subtypes

No approved agents or treatments for peripheral T- cell lymphoma

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0

5

10

15

20

25

30

Evaluable T-cell Lymphoma Patients

PDX: Phase 1/2 PTCL Clinical Results 2007 AACR-NCI-EORTC Conference

Summary Interim Phase 1/2 Results

• Favorable activity observed in heavily pre-treated PTCL patients

• 54% of evaluable patients (14 of 26) achieved response

• Duration of response typically exceeded that of prior line of chemotherapy

• Mucositis mitigated by vitamins and correlated with MMA, Hcy levels and AUC of PDX exposure

• Other major toxicities were thrombocytopenia and leukopenia

• Recommended Phase 2 dose is 30 mg/m2 weekly x 6

Source: O’Connor et al. AACR-NCI-EORTC 2007 Conference

Did not achieve

CR or PR(n=12)

Complete response

(n=9)

Partial response

(n=5)

(N=26)

54% RR

Achieved durable responses in pre-treated PTCL patients

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Duration of responseProgression-free survivalOverall survival

Secondary Endpoints

Response RatePrimary Endpoint

30 mg/m2 of PDX weekly x 6 then 1 week rest1 mg vitamin B12 intramuscular every 8 – 10 weeks; 1 mg folic acid by mouth once a day

Treatment

At least 100 evaluable patientsNumber of Patients

Adult patients with relapsed or refractory PTCLTarget Population

Single arm, open label, multi-centerTrial Design

PROPEL: Pivotal Phase 2 Trial in PTCL

Trial Conducted Under FDA SPA; PDX Granted Fast Track Designation

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02468

101214161820

PROPEL: Pivotal Phase 2 Study in PTCL65-Patient Interim Data

• Heavily pre-treated patients• Median of 3 prior treatment regimens

• 29% response rate in first 65 evaluable patients as assessed by central independent review

• 45% response rate in first 65 evaluable patients as assessed by PROPEL investigators

• Median duration of response cannot be estimated due to current length of follow up

• Most common drug-related grade 3/4 adverse events:

• Mucositis – 14%• Thrombocytopenia – 23%

Source: Allos Press Release – May 15, 2008

First 65 Evaluable Patients

*A patient is considered evaluable if the patient received at least one dose of PDX and their diagnosis of PTCL has been confirmed by independent review.

19

Responders

29% Response Rate

# P

atie

nt R

espo

nses

(CR

+PR

)

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PROPEL: Key Clinical & Regulatory Milestones

Reached agreement under FDA’s SPA process Jul 2006

Initiated patient enrollment Aug 2006

Received FDA’s fast track designation Oct 2006

Positive outcome of 10-patient safety assessment Jan 2007

Positive outcome of 35-patient safety & response assessment Sep 2007

Positive outcome of 65-patient safety assessment Dec 2007

Completed patient enrollment Apr 2008

Reported 65-patient interim response data May 2008

Expected to report top line results YE 2008

File NDA as Expeditiously as Possible

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PDX: Expanded Lymphoma Development

Determine MTDEvaluate safety and tolerabilityDetermine PK profileAssess preliminary efficacy in PTCL patients

Objectives

PDX followed the next day by gemcitabine weekly x 2 or 3 with 1 week rest 1 mg vitamin B12 intramuscular every 8 – 10 weeks and 1 mg folic acid by mouth once a day

Treatment

Up to 54 patients in Phase 1Up to 30 PTCL patients - Phase 2

Number of Patients

Adult patients with relapsed or refractory NHL or Hodgkin’s disease

Target Population

Single-arm, open-label, multi-centerStudy Design

Determine optimal dose & scheduleEvaluate safety and tolerability

Objectives

PDX weekly x 2 or 3 with 1 week rest

1 mg vitamin B12 intramuscular every 8 – 10 weeks and 1 mg folic acid by mouth once a day

Treatment

Up to 56 patientsNumber of Patients

Adult patients with relapsed or refractory CTCL

Target Population

Single-arm, open-label, multi-centerStudy Design

Phase 1/2a study: PDX + gemcitabine in NHL Phase 1 study: PDX in CTCL

Interim Study Updates Expected by Year End

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PDX: Compelling Solid Tumor Opportunity

Under Evaluation

Under Development

Demonstrated antifolate clinical activity; no investigational agent superior to MTX head-to-headHigh unmet medical need; MST for Stage III/IV approximately 6 mos.

25,125Head & Neck: Stage III/IV

10-deaza-aminopterin demonstrated activity: 21% RRMTX actively used 1st and 2nd lineNo approved treatments/no SOC/unmet medical need

8,900Bladder: Stage III/IV

MTX well established in adjuvant settingCytotoxics utilized up to 4th – 5th lines of therapy

31,730Breast: Stage III/IV

PDX activity in relapsed NSCLC comparable to approved agents: 11% RR w/o vitamins, TTP: 3 mos.High unmet medical need: 5-yr survival rate for Stage IIIB/IV approximately 15%

98,950NSCLC: Stage IIIB/IV

Clinical and Commercial Rationale2007 U.S. Incidence

Tumor type

Incidence source: Decision Resources 2006

Potential for expanded development of PDX in solid tumors

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PDX: Prior Advanced NSCLC Clinical Results

Addition of vitamins to PDX treatment regimen enabled higher dosing, which may lead to greater therapeutic benefit

Phase 2 study of PDX in relapsed/refractory stage IIIB/IV NSCLC without vitamin supplementation; MTD 135 mg/m2

• 11% response rate

• 13.5 months median survival

• 3 months median time to progression

• Grade 3/4 stomatitis – 21% of patients

Subsequent Phase 1 study- PDX w/ vitamin supplementation; MTD 270 mg/m2

• Data presented at AACR-NCI-EORTC 2007 Conference

• Previously treated Stage IIIB/IV NSCLC patients

• Clinically significant radiologic responses observed

• Recommended Phase 2 starting dose – 190 mg/m2

Krug LM, Azzoli CG, Kris MG, et al. 10-propargyl-10-deazaaminopterin: an antifolate with activity in patients with previously treated non-small cell lung cancer. Clin Cancer Res 2003;9(6):2072-8.

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PDX: Phase 2b Advanced NSCLC Study

Response rateProgression-free survivalSafety and tolerability

Secondary Endpoints

Overall survivalPrimary Endpoint

PDX arm: - 190 mg/m2 which may be increased to 230 mg/m2 or reduced in 40 mg/m2 decrements- IV push on days 1 and 15 of a 4-week/28 day cycleTarceva arm: - 150 mg/day orally daily for a 4-week/28 day cycleConcurrent vitamin supplementation: - B12 (1mg intramuscular every 8-10 weeks)- Folic acid (1 – 1.25 mg by mouth once a day)

Treatment

A minimum of 160 evaluable patientsNumber of Patients

Stage IIIB/IV non-small cell lung cancer (NSCLC) who are, or have been, cigarette smokers who have failed treatment with at least one prior platinum-based chemotherapy regimen

Target Population

Randomized, multi-center study comparing PDX to TarcevaStudy Design

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Product Development Pipeline

Preclinical Phase 1 Phase 2 Phase 3 NDA MarketPDX

Peripheral T-cell Lymphoma

Additional Indication

Non-Hodgkin’s Lymphoma

B-cell Non-Hodgkin’s Lymphoma

PDX + Gemcitabine

Cutaneous T-cell Lymphoma

RH1

ongoing planned

Non-small Cell Lung Cancer

HEMATOLOGIC MALIGNANCIES

SOLID TUMORS

PROPEL: SPA approved, registration trial

Solid Tumors/NHL

(Phase 2)

(Phase 1/2)

(Phase 1/2a)

(Phase 1)

(Phase 2b)

(Phase 2)

(Phase 1)

PDX vs. Erlotinib

Non-small Cell Lung Cancer(Phase 1)

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RH1: Targeted Cytotoxic Prodrug

Targeted cytotoxic prodrug bioactivated by enzyme DT-diaphorase (DTD)

Over-expressed predominantly in lung, colon, liver and breast

Cytotoxicity caused by DNA cross-linking

Cancer Research UK completed Phase 1 dose escalation study in patients with solid tumors refractory to other chemotherapy regimens*

Company sponsored Phase 1 dose escalation study in patients withadvanced solid tumors and NHL initiated in November 2007

Determine maximum tolerated dose (MTD)Determine recommended Phase 2 doseAssess safety profile

*Source – “Final results of a phase I clinical trial of the bioreductive drug RH1”, S. Danson – 2007 ASCO Annual Conference

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Commercial Considerations

Exclusive worldwide commercial rights to PDX & RH1 for all indications

Oncology market is attractive due to its:SizeUnmet demand for safer and more effective treatmentsRelatively small physician populationPotential for expedited regulatory review

Moderate-sized oncology focused sales & marketing organization may effectively reach targeted physicians and medical institutions that treat the majority of patients with PTCL

Potential for co-promotion or out-licensing to reach ex-US markets

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Financial Summaryin millions and unaudited

Cash at March 31, 2008 $ 50.5

Net cash used in operating activities for quarter ended 3/31/08 $ (9.3)

Shares outstanding at May 1, 2008 68.1

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Key Achievements & Upcoming Milestones

2008Initiated Phase 2b study of PDX in NSCLC Jan

Completed PROPEL patient enrollment Apr

Reported PROPEL 65-patient interim data May

Expect to report CTCL interim data Jun

Expect to initiate Phase 2 study of PDX Q2 in additional solid tumor indication

Expect to initiate additional PDX studies YE

Expect to report B-cell interim data YE

Expect to report additional CTCL data YE

Expect to report PROPEL top line results YE

2007Positive outcome of PROPEL10-patient interim safety assessment Jan

EMEA Orphan Medicinal Product designation for PDX in PTCL Apr

Initiated Phase 1/2 study of PDX plus Gemcitabine in NHL May

Initiated Phase 1 study of PDX in CTCL Aug

Positive outcome of PROPEL 35-patient response & safety assessment Sep

Reported results from Phase 1 study of PDX in NSCLC Oct

Initiated Phase 1 study of RH1 in solid tumors/NHL Nov

Positive outcome of PROPEL 65-patient interim safety assessment Dec

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Investor Presentation

May 2008

NASDAQ: ALTH

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Management teamPaul BernsPresident and CEO

Dr. Pablo CagnoniChief Medical Officer

James CarusoChief Commercial Officer

Marc GraboyesGeneral Counsel

Bruce BennettVice President, Manufacturing

David ClarkVice President, Finance